Also moved the #defines for linkage types into a separate header instead of
mars.h so we can #include revisions.h without having to rebuild the entire
frontend every time we update.
(I'm using revisions.h to get the LLVM revision for use in preprocessor
conditionals. It should work with LLVM release 2.5, old trunk and new trunk)
If the user has patches managed by the mq extension, the version and hash
printed are those of the qparent revision (the revision the patches were
applied on top of) instead of tip.
Also fixes a bug: print LLVM revision even if there are local modifications to
it.
Sorry for the long line in the perl file. I have no idea how to break it up.
