Work around Subversion race in git-svn tests.

Work around Subversion race in git-svn tests.

Some of the git-svn tests can fail on fast machines due to a race in
Subversion: if a file is modified in the same second it was checked out
(or in for that matter), Subversion will not consider it modified. This
works around the problem by increasing the timestamp by one second
before each commit.

[jc: with "touch -r -d" replacement from Eric]

Acked-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Michael Spang <mspang@uwaterloo.ca>
Signed-off-by: Junio C Hamano <junkio@cox.net>