Add basic log filtering

This enables case-insensitive grep on logentris using the new search box

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

cgit.h

@@ -104,7 +104,7 @@ extern void cgit_print_pageheader(char *title, int show_search);
 
 extern void cgit_print_repolist(struct cacheitem *item);
 extern void cgit_print_summary();
-extern void cgit_print_log(const char *tip, int ofs, int cnt);
+extern void cgit_print_log(const char *tip, int ofs, int cnt, char *grep);
 extern void cgit_print_view(const char *hex);
 extern void cgit_print_tree(const char *hex);
 extern void cgit_print_commit(const char *hex);