Add knobs to enable/disable files/lines changed in log view

These columns can cause lots of IO on the server, so add settings to
explicitly enable them. Also, add per repo settings to optionally disable
the columns if sitewide enabled.

While at it, do not allow repo.snapshot to enable snapshots if the global
setting is disabled.

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

cgit.h

@@ -38,6 +38,8 @@ struct repoinfo {
 	char *defbranch;
 	char *module_link;
 	int snapshots;
+	int enable_log_filecount;
+	int enable_log_linecount;
 };
 
 struct repolist {
@@ -81,6 +83,8 @@ extern char *cgit_cache_root;
 
 extern int cgit_nocache;
 extern int cgit_snapshots;
+extern int cgit_enable_log_filecount;
+extern int cgit_enable_log_linecount;
 extern int cgit_max_lock_attempts;
 extern int cgit_cache_root_ttl;
 extern int cgit_cache_repo_ttl;