Add support for config param summary-branches

This parameter can be used to specify max number of branches to show
on the summary page (if not all branches will be displayed, the "most
idle" branches are the ones to be pruned). The default value for this
parameter is 0, which disables the pruning.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

shared.c

@@ -39,6 +39,7 @@ int cgit_cache_static_ttl      = -1;
 int cgit_cache_max_create_time =  5;
 int cgit_summary_log           =  0;
 int cgit_summary_tags          =  0;
+int cgit_summary_branches      =  0;
 int cgit_renamelimit           = -1;
 
 int cgit_max_msg_len = 60;
@@ -182,6 +183,8 @@ void cgit_global_config_cb(const char *name, const char *value)
 		cgit_max_commit_count = atoi(value);
 	else if (!strcmp(name, "summary-log"))
 		cgit_summary_log = atoi(value);
+	else if (!strcmp(name, "summary-branches"))
+		cgit_summary_branches = atoi(value);
 	else if (!strcmp(name, "summary-tags"))
 		cgit_summary_tags = atoi(value);
 	else if (!strcmp(name, "agefile"))