[PATCH] ogg.m4 is not friendly to disabling

some projects have optional ogg support. like a good project, they just use the ogg.m4 that is provided by libogg. that's when they get screwed :).

ogg.m4 does not provide a way for the user to explicitly state "i do not want ogg support". i've cleaned up the ogg.m4 so that if you do --without-ogg, you get the expected behavior. i've also fixed the case where doing --with-ogg causes broken -I/-L flags to get added (yes/lib and yes/include)