svn revision information

[Joseph Parker]

GS2 tries to use the svn revision number at various points, most notably in Makefile, build_gs2 and in some scripts and tests. These should be replaced with git revision information.

The branch git_info starts doing this, replacing the SVN_REV compiler flag with GIT_HASH for the hash, and GIT_STATE for whether the working tree is clean or modified. (I think this code originally came from @daviddickinson)

[Stephen Biggs-Fox]

FYI - If you try to build GS2 on a machine where subversion is not installed, you get messages to stderr saying "make: svnversion: Command not found" before each compile command. Obviously this will be fixed by addressing this issue (or, in the short term, installing subversion).

[David Dickinson]

I think this has been resolved by PR #7.

[Joseph Parker]

Resolved by PR #7