Clcache

* Feature: Enable installation directly from GitHub via 'pip install'
* Bugfix: Fixed potential corruption of cache in case clcache is terminated
while writing a cache entry or updating the cache statistics.
* Internal: The automatic clcache tests are now executed with Python 3.6, too.
* Internal: Support for Python 3.3 and Python 3.4 has been dropped.
* Bugfix: Fixed invoking the real compiler when using the `/Tc` or `/Tp`
switches (GH 289)
* Feature: Allow specifying just a file name via `CLCACHE_CL`, the absolute
path will be computed automatically by scanning the `PATH`.
* Bugfix: clcache correctly honours termination signals such as Ctrl+C again
(GH 261).
* Bugfix: Fixed some cases in which clcache might have written corrupted cache
entries in case it gets terminated in the middle of copying a file (GH 263).
* Feature: Added 'monkey' script to simplify integrating clcache with distutils-based
workflows (GH 284).
* Feature: Drop version in directory structure of chocolatey (nuget) target
package (GH 318).

* Bugfix: Fixed resource leak in clcachesrv.
* Improvement: clcachesrv now shuts down cleanly when receiving SIGTERM.
* Feature: clcachesrv now supports blacklisting directories to watch for file
changes; this avoids problems with deleting such directories because clcachesrv
still has them opened (in order to get notified to changes to header files).
* Internal: The clcache source code now passes the checks performed by pylint 1.7.1
* Documentation: Installation & integration instructions have been moved from
the README file, into the clcache wiki at https://github.com/frerich/clcache/wiki
* Feature: clcache now supports using a [memcached](https://memcached.org/)
setup as the storage mechanism in addition to storing cached files in the file
system.

* Bugfix: Fixed occasional 'Cannot create a file when that file already
exists' error when adding new objects to the cache (GH 155).
* Improvement: Extended handling of CLCACHE_BASEDIR variable to improve cache
hit rates when using different build directories.
* Improvement: Improved interaction between concurrent clcache invocations
when encountering multiple cache misses in parallel; the risk of triggering
timeout exceptions is greatly reduced (GH 229).
* Bugfix: Improved error handling in case statistics files or manifest files
in the cache are malformed, which could happen when clcache got terminated
abnormally.
* Bugfix: Fixed off-by-one error when compiling source files concurrently,
clcache would always launch one concurrent instance more than intended.
* Feature: Added support for a 'CLCACHE_SERVER' environment variable which, when
set to '1', makes 'clcache' use a separate 'clcachesrv' server process to cache
hash sums. This improves performance, especially so for warm caches.
* Improvement: Improved performance when invoking clcache with multiple source
files; it will no longer launch itself recursively but rather use multiple
threads to process the individual source files.
* Internal: clcache now uses semantic versioning.

* Bugfix: Aborting clcache via Ctrl+C or SIGTERM will no longer have the risk
of leaving the cache in a defective state.
* Internal: Fixed running integration tests when the clcache source code is
stored in a path with spaces (GH 206).
* Improvement: Optimized communicating with real compiler.
* Bugfix: Fixed a potential CacheLockException apparently caused by
a race condition between calling CreateMutexW() and
WaitForSingleObject().

* Bugfix: /MP no longer causes a greatly reduced cache hit rate.
* Bugfix: In direct mode, clcache will no longer try to access non-existant
header files (GH 200, GH 209).
* Bugfix: Correctly cache and restore stdout/stderr output of compiler when
building via the Visual Studio IDE.
* Add support for the `CL` and `_CL_` environment variables (GH 196).
* Feature: A new `CLCACHE_PROFILE` environment variable is now recognised
which can be used to make clcache generate profiling information. The
generated data can be processed into a final report using a new
`showprofilereport.py` script.
* Improvement: Timeout errors when accessing the cache now generate friendlier
error messages mentioning the possibility to work around the issue using the
`CLCACHE_OBJECT_CACHE_TIMEOUT_MS` environment variable.
* Improvement: Greatly improved concurrency of clcache such that concurrent
invocations of the tool no longer block each other.
* Improvement: Improve hit rate when alternating between two identical
versions of the same source file that transitively get different contents of
the included files (a common case when switching back and forth between
branches).

* Bugfix: When preprocessing was used together with an /Fo argument (which makes
no sense), the handling was wrong.
* Bugfix: Properly handle /Fi arguments
* Bugfix: Fixed printing cached compiler output when using Python 2.x.
* Dropped support for caching preprocessor invocations. The number of such
invocations is now printed in the statistics (`ccache -s`).
* Bugfix: In MSVS, arguments use the formats `/NAMEparameter` (no space, required value),
`/NAME[parameter]` (no space, optional value), `/NAME[ ]parameter` (optional space),
and `/NAME parameter` (required space). Before we always tried `/NAMEparameter`
and if there if no parameter, tried `/NAME parameter`. This strategy was too simple
and failed for like e.g. `/Fo`, which must not consume the following argument when
no parameter is set.
* Rework manifests: use JSON to store manifests. This makes all existing manifests
invalid. Cleaning and clearing now removes old manifest files as well, so the old
.dat files are automatically removed.
* clcache now requires Python 3.3 or newer.
* py2exe support was dropped, PyInstaller is now recommended for generating
.exe files.