Benchexec

- In container mode, all temp directories are now on a `tmpfs` "RAM disk".
This affects everything written to directories in the hidden or overlay modes.
Files written there are now included in the memory measurements and the memory limit!
The advantage is that performance should be more deterministic,
especially if several runs use much I/O in parallel.
This feature can be disabled with `--no-tmpfs`.
- `/dev/shm` and `/run/shm` are now available inside the container
and provide a `tmpfs` instance (even with `--no-tmpfs`)
as required by some tools for shared memory.
- Container mode now recommends [LXCFS](https://github.com/lxc/lxcfs)
and automatically uses it if available for a better container isolation
(e.g., uptime measures container uptime, not host uptime).
On Debian/Ubuntu, just use `sudo apt install lxcfs`.
- Several small bug fixes and other improvements of isolation for container mode
(e.g., host name in container is no longer the real host name).
- Add `benchexec --no-hyperthreading`, which restricts core assignments
to a single virtual core per physical CPU core
(all other sibling cores will stay unused).
Thanks [alohamora](https://github.com/alohamora)!

- Add result `done` that tools can output if the standard results `true`/`false`/`unknown`
are not applicable (for example because no property was checked),
and the run completed successfully.
- In container mode, `--keep-system-config` is no longer necessary if overlayfs
is not used for `/etc`, and thus it is is no longer automatically implied in such cases.
- Benchmark definitions support a new attribute `displayName` with a human-readable name
that will be shown in tables.
- A new variable `${taskdef_name}` can now be used in places where variable substitution is supported.
- Table-generator supports `%` as unit for numerical values.
- Some improvements for score handling outside of SV-COMP (i.e., if scores are not calculated by BenchExec).
- New tool-info modules for Test-Comp'19
- Several small bug fixes and improvements

- Tasks can now be defined in a YAML-based format,
cf. [the documentation](https://github.com/sosy-lab/benchexec/blob/master/doc/benchexec.md#task-definition-files)
This supports tasks with several input files,
and allows providing metadata such as expected verdicts
in a structured format instead of encoded in the file name.
The format will be extended to handle more information in the future.
- The wall-time limit can now be specified separately from the CPU-time limit
for `benchexec` as command-line parameter or in the benchmark definition.
- Support for SV-COMP'19 property `memcleanup`.
- In containers, properly handle `/run/systemd/resolve`,
which is necessary for DNS resolution on systems with `systemd-resolved`.
- Avoid warnings for mountpoints below inaccessible directories in containers.
- Improvements for handling `NaN` and `Inf` values in `table-generator`.
- Log output of BenchExec will now have colors if `coloredlogs` is installed.
- New tool-info modules and updates for SV-COMP'19.

- Support for [energy measurements](https://github.com/sosy-lab/benchexec/blob/master/doc/resources.md#energy)
if [cpu-energy-meter](https://github.com/sosy-lab/cpu-energy-meter) is installed.
- Several small bug fixes and improvements

- Updated tool-info modules for all participants of [SV-COMP'18](https://sv-comp.sosy-lab.org/2018/).
- Extended support for variable replacements in table-definitions
of table-generator.