Allow to use new GD-2.1.0 function from system library
Remove overflow2, getmbi and skipheader, since they are not needed anymore.
* Remove overflow2, getmbi and skipheaders from gd_compat.h * Add missing return in _php_ctx_getmbi * Reintroduce imagecreatefromxbm by checking for gdCreateImageFromXbm
Required GD >= 2.1.0 or GD bundled, this allows us to remove most of the #ifdef
Rewrite Xpm library check so it doesn't break on MultiArch systems
Remove extra unused functions from gd_compat.h
Move png and jpeg version functions to gd.c so the external library build doesn't include anything from libgd/.
fix build with bundled libgd
NEWS