git-gui: reinstate support for Tcl 8.4
Tcl 8.5 introduced an extended vsatisfies syntax that is not
supported by Tcl 8.4.
Since only Tcl 8.4 is required this presents a problem.
The extended syntax was used starting with Git 2.0.0 in commit
b3f0c5c0 (git-gui: tolerate major version changes when comparing the
git version, 2014-05-17), so that a major version change would still
satisfy the condition.
However, what we really want is just a basic version compare, so use
vcompare instead to restore compatibility with Tcl 8.4.
Signed-off-by: Kyle J. McKay <mackyle@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>