This should hopefully fix the issue where WITH_SDL can be defined while SDL-CONFIG is not
Added an error if WITH_SDL is defined but SDL-CONFIG is not. The same goes for WITH_PNG even though nobody reported this as a problem
removed STATIC_ZLIB_PATH as it turns out that nobody used it
if detected, WITH_ICONV will be defined in the C code
WITH_ICONV is also added to Makefile.config
OSX do not use this flag setting in Makefile.config, as it is set at compile time based on target OS version
the actual C code is not changed as the current iconv code is hardcoded for OSX and would break if any other OS got iconv
This detection system is by request of Darkvater
you can still use SDL drivers if you like and you have to run "make upgradeconf" to start using the cocoa drivers (or manually write WITH_COCOA:=1)
since SDL breaks the cocoa drivers, you can't compile with both SDL and cocoa support
Using cocoa drivers makes it easier to make universal binaries and it solves:
-FS#18 [OSX] SDL is weird in universal binaries
-FS#2 [OSX] lazy pointer crash on exit
-FS#10 [OSX] linking error when linking statically to SDL 1.2.8 (needless to explain this, but it means it should be able to compile statically with the default settings now)
-[ 1215073 ] Switching to large size out of fullscreen crashes
Using SDL drivers will still have those issues though
This is not a fix for the issues with static linking, more like a workaround. Static linking still got issues
Apple recommends to use dynamic linking anyway, so I guess this doesn't matter much
