Revert "Merge branch 'flats-png_port' into 'master'"

src/doomdef.h

src/hardware/hw_cache.c

src/hardware/hw_glide.h

src/hardware/hw_glob.h

src/hardware/hw_light.c

src/hardware/hw_main.c

src/hardware/hw_md2.c

src/p_setup.c

src/p_setup.h

src/p_spec.c

src/r_data.c

src/r_data.h

src/r_draw.c

src/r_draw.h

src/r_draw8.c

src/r_plane.c

src/r_plane.h

src/screen.c

src/w_wad.c