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 <jmccrohan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-instaweb.sh

@@ -345,7 +345,17 @@ PidFile "$fqgitdir/pid"
 Listen $bind$port
 EOF
 
-	for mod in mime dir env log_config
+	for mod in mpm_event mpm_prefork mpm_worker
+	do
+		if test -e $module_path/mod_${mod}.so
+		then
+			echo "LoadModule ${mod}_module " \
+			     "$module_path/mod_${mod}.so" >> "$conf"
+			# only one mpm module permitted
+			break
+		fi
+	done
+	for mod in mime dir env log_config authz_core
 	do
 		if test -e $module_path/mod_${mod}.so
 		then