Prevent conflicts when linking both SDL2 and SDL2_gfx
Fixed bug 2129 - fix for bug 2121 breaks linking for mingw and throws multiple warnings

Andreas Ertelt

The problem in question is caused by changeset 7771 (http://hg.libsdl.org/SDL/rev/4434498bf4b9 / https://bugzilla.libsdl.org/show_bug.cgi?id=2121)

The redefinition of __inline__ (introduced by the addition of begin_code.h:128's "|| __STRICT_ANSI__") results in mingw's gcc throwing multiple

   warning: always_inline function might not be inlinable [-Wattributes]

as well as a whole bunch of redefinitions of mingw internals which break linking of projects including the SDL2 headers.