Parakeet

- Added OpenMP backend (runs most map-like computations across multiple threads)
- Stack-allocate representations for all structured types in C
- Disabled Flattening -- tricky transform needs careful audit
- Debugged and enabled CopyElimination
- Fixed negative step in slices
- Added RLock around AST translation to play nice with Python threads (thanks Russell Power)
- Fixed link argument order for building on cygwin in Windows (thanks Yves-Rémi Van Eycke)

- Added support for binding multiple variables in a for loop (i.e. "for (x,(y,z)) in enumerate(zip(ys,zs)):")
- More array constructors support 'dtype' argument
- macros can now generate wrapper functions with keyword arguments
- lib_helpers._get_type can pull element types out of a wider range of values
- Added more unit tests from Python benchmarks
- Added option to manually specify compiler in c_backend.config.compiler_path
- Slightly better support for negative indexing but negative step sizes are still mostly broken

- Moved version info into submodule so setup.py can run without full dependencies (thanks rjpower).
- Fixed support for references to global arrays.
- Make C backend respect runtime changes to config flags.
- Got rid of unncessary linking against libpython.

- Fixed bugs in C backend and a several optimizatons.
- Only print stderr if C backend fails to compile.

- Added flattening transformation which gets rid of all structures except scalars and pointers.
- Created new C backend which compiles with either gcc or clang.
- Disabled some of the more powerful optimizations (i.e. scalar replacement) which might introduce bugs.
- Revamped the optimization pipeline to avoid running duplicate transformations and allow for better logging.
- "Indexify" all adverbs by turning them into ParFor/IndexReduce/IndexScan.