[PATCH] Clean up remaining signedness issues

Recent versions of gcc on Linux, e.g. gcc on Debian/sarge (or rather, Debian/testing) complains a lot, making warnings less useful for easily spotting problems. The bulk of the warnings is taken care of in the incompatible_pointer patches, this cleans up the rest. After this, Icecast is -Wall clean on Linux again.

While around in src/util.c, fix up some int->size_t's.