git-instaweb: add support for Apache 2.4
git-instaweb: add support for Apache 2.4

Detect available Apache MPMs and use first available according to
following order of precedence:
mpm_event
mpm_prefork
mpm_worker

Add authz_core module if available to avoid HTTP Error 500 errors.

Signed-off-by: Jonathan McCrohan <570a29e1a0f65cf1fa3e2f066525eecae621874c@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git