* vc.el (vc-log-show-limit): New variable.

* vc.el (vc-log-show-limit): New variable.
(vc-print-log, vc-print-root-log): Add new argument LIMIT.  Set it
when using a prefix argument.
(vc-print-log-internal): Add new argument LIMIT.

* vc-svn.el (vc-svn-print-log):
* vc-mtn.el (vc-mtn-print-log):
* vc-hg.el (vc-hg-print-log):
* vc-bzr.el (vc-bzr-print-log): Add new optional argument LIMIT,
pass it to the log command when set. Make the BUFFER argument
non-optional.

* vc-sccs.el (vc-sccs-print-log):
* vc-rcs.el (vc-rcs-print-log):
* vc-git.el (vc-git-print-log):
* vc-cvs.el (vc-cvs-print-log): Add new optional argument LIMIT,
ignore it.  Make the BUFFER argument non-optional