Bump copyright
Trying to lock cache directory consistently

Executing clcache.py in parallel might cause race conditions when
accessing the cache directory. All access to the cache directory
needs to be synchronized, so we need to implement some kind of
locking. Maybe I should rather use a simple SQL database or the
like which gets me ACID semantics for free...
Made findCompilerBinary() more robust in case we were frozen using py2exe

When using py2exe, it may well be that the user renamed the resulting
binary to 'cl.exe' so that it's a drop-in replacement. In that case,
we need to be more careful when trying to find the real compiler binary
because it's very well possible that the first cl.exe binary we find
is ourselves. If we used that, we'd invoke ourselves recursively.
Prefer using py2exe over a simple batch file

It seems that most people just compile to an executable to get a
drop-in replacement for cl.exe. Many build tools out there seem to get
a little confused in case the compiler binary is a batch file.
When parsing response files, don't swallow backslashes

I'm not quite sure how shlex behaves but in Posix mode a backslash
is treated as an escape character. Which is not the right thing for
me, I think on Windows '^' is the escape character.