extended support for git repos:
generate numeric version from last commit date,
record host, remote and branch names
svn path=/trunk/boinc/; revision=23213
- generate version string from plain git repositories, too (from Oliver)
- define SVN_REPOSITORY (URL) and SVN_REVISION (numerical) separately
so these could be used in proprocessor directives
svn path=/trunk/boinc/; revision=22905