Py-gfm

* Added commonmark renderer: `cmark_render_commonmark`. In addition
to options, this takes a `width` parameter. A value of 0 disables
wrapping; a positive value wraps the document to the specified
width. Note that width is automatically set to 0 if the
`CMARK_OPT_HARDBREAKS` option is set.
* The `cmark` executable now allows `-t commonmark` for output as
CommonMark. A `--width` option has been added to specify wrapping
width.
* Added `roundtrip_test` Makefile target. This runs all the spec
through the commonmark renderer, and then through the commonmark
parser, and compares normalized HTML to the test. All tests pass
with the current parser and renderer, giving us some confidence that
the commonmark renderer is sufficiently robust. Eventually this
should be pythonized and put in the cmake test routine.
* Removed an unnecessary check in `blocks.c`. By the time we check
for a list start, we've already checked for a horizontal rule, so
we don't need to repeat that check here. Thanks to Robin Stocker for
pointing out a similar redundancy in commonmark.js.
* Fixed bug in `cmark_strbuf_unescape` (`buffer.c`). The old function
gave incorrect results on input like `\\*`, since the next backslash
would be treated as escaping the `*` instead of being escaped itself.
* `scanners.re`: added `_scan_scheme`, `scan_scheme`, used in the
commonmark renderer.
* Check for `CMAKE_C_COMPILER` (not `CC_COMPILER`) when setting C flags.
* Update code examples in documentation, adding new parser option
argument, and using `CMARK_OPT_DEFAULT` (Nick Wellnhofer).
* Added options parameter to `cmark_markdown_to_html`.
* Removed obsolete reference to `CMARK_NODE_LINK_LABEL`.
* `make leakcheck` now checks all output formats.
* `test/cmark.py`: set default options for `markdown_to_html`.
* Warn about buggy re2c versions (Nick Wellnhofer).

* Build static version of library in default build (11).
* `cmark.h`: Add missing argument to `cmark_parser_new` (12).

* Switch to 2-clause BSD license, with agreement of contributors.
* Added Profile build type, `make prof` target.
* Fixed autolink scanner to conform to the spec. Backslash escapes
not allowed in autolinks.
* Don't rely on strnlen being available (Nick Wellnhofer).
* Updated scanners for new whitespace definition.
* Added `CMARK_OPT_SMART` and `--smart` option, `smart.c`, `smart.h`.
* Added test for `--smart` option.
* Fixed segfault with --normalize (closes 7).
* Moved normalization step from XML renderer to `cmark_parser_finish`.
* Added options parameter to `cmark_parse_document`, `cmark_parse_file`.
* Fixed man renderer's escaping for unicode characters.
* Don't require python3 to make `cmark.3` man page.
* Use ASCII escapes for punctuation characters for portability.
* Made `options` an int rather than a long, for consistency.
* Packed `cmark_node` struct to fit into 128 bytes.
This gives a small performance boost and lowers memory usage.
* Repacked `delimiter` struct to avoid hole.
* Fixed use-after-free bug, which arose when a paragraph containing
only reference links and blank space was finalized (9).
Avoid using `parser->current` in the loop that creates new
blocks, since `finalize` in `add_child` may have removed
the current parser (if it contains only reference definitions).
This isn't a great solution; in the long run we need to rewrite
to make the logic clearer and to make it harder to make
mistakes like this one.
* Added 'Asan' build type. `make asan` will link against ASan; the
resulting executable will do checks for memory access issues.
Thanks JordanMilne for the suggestion.
* Add Makefile target to fuzz with AFL (Nick Wellnhofer)
The variable `$AFL_PATH` must point to the directory containing the AFL
binaries. It can be set as an environment variable or passed to make on
the command line.

* Stripped out all JavaScript related code and documentation, moving
it to a separate repository (<https://github.com/jgm/commonmark.js>).
* Improved Makefile targets, so that `cmake` is run again only when
necessary (Nick Wellnhofer).
* Added `INSTALL_PREFIX` to the Makefile, allowing installation to a
location other than `/usr/local` without invoking `cmake`
manually (Nick Wellnhofer).
* `make test` now guarantees that the project will
be rebuilt before tests are run (Nick Wellnhofer).
* Prohibited overriding of some Makefile variables (Nick Wellnhofer).
* Provide version number and string, both as macros
(`CMARK_VERSION`, `CMARK_VERSION_STRING`) and as symbols
(`cmark_version`, `cmark_version_string`) (Nick Wellnhofer). All of
these come from `cmark_version.h`, which is constructed from a
template `cmark_version.h.in` and data in `CMakeLists.txt`.
* Avoid calling `free` on null pointer.
* Added an accessor for an iterator's root node (`cmark_iter_get_root`).
* Added user data field for nodes (Nick Wellnhofer). This is
intended mainly for use in bindings for dynamic languages, where
it could store a pointer to a target language object (287). But
it can be used for anything.
* Man renderer: properly escape multiline strings.
* Added assertion to raise error if finalize is called on a closed block.
* Implemented the new spec rule for emphasis and strong emphasis with `_`.
* Moved the check for fence-close with the other checks for end-of-block.
* Fixed a bug with loose list detection with items containings
fenced code blocks (285).
* Removed recursive algorithm in `ends_with_blank_line` (286).
* Minor code reformatting: renamed parameters.

* Added xml renderer (XML representation of the CommonMark AST,
which is described in `CommonMark.dtd`).
* Reduced size of gperf entity table (Nick Wellnhofer).
* Reworked iterators to allow deletion of nodes during iteration
(Nick Wellnhofer).
* Optimized `S_is_leaf`.
* Added `cmark_iter_reset` to iterator API.
* Added `cmark_consolidate_text_nodes` to API to combine adjacent
text nodes.
* Added `CMARK_OPT_NORMALIZE` to options (this combines adjacent
text nodes).
* Added `--normalize` option to command-line program.
* Improved regex for HTML comments in inline parsing.
* Python is no longer required for a basic build from the
repository.

* No feature change.
* Pin Markdown dependency to <3.0, as Markdown 3.0 introduced breaking changes
to its internal API (issue 13). A future release of py-gfm that is compatible
with Markdown ≥3.0 is planned, with no ETA.