Clarify new semantics of cache size settings
Document direct mode
Fix flymake-mode support again
Improve handling of -imacros, -iprefix and -i*prefix* compiler options
Bail out on @file_with_options argument
Clarify cache size limit options' semantics
Create temporary manifest files in the directory they will end up in

See also commit 106566bb638d112826fafa1661259258ac6ac1f7.
Use uint32_t magic/version constants
Truncate the manifest if there are too many object entries

Normally, there shouldn't be many object entries in the manifest since new
entries are added only if an include file has changed but not the source file,
and you typically change source files more often than header files. However,
it's certainly possible to imagine cases where the manifest will grow large
(for instance, a generated header file that changes for every build), and this
must be taken care of since processing an ever growing manifest eventually will
take too much time. A good way of solving this would be to maintain the object
entries in LRU order and discarding the old ones. An easy way is to throw away
all entries when there are too many. Let's do that for now.
Sort environment variable documentation entries
Document CCACHE_BASEDIR
Consistently refer to options, not flags
Include NEWS in the dist archive
Improve NEWS
Fix typo
Handle empty arguments correctly
announce new maintainer and add git instructions

Joel Rosdahl is now the maintainer of ccache. Best wishes Joel!
Made it possible to set MYNAME when compiling
Bump version to 3.0pre0
Add some simple README and INSTALL files