Fixed so many things. See the changelog listed below. 1. Use SDL_X11_HAVE_XRENDER to check for RENDER at runtime. 2. Added lots of comments. 3. Added checks and lots of calls to SDL_SetError(). 4. Fixed X11_CreateTexture() so that the pixmap and image created are for the format specified by the user and not the window format. This is only for the RENDER case. 5. The above change required that functions to convert SDL pixel format enums to Visuals and XRenderPictFormats be added. 6. Fixed lots of 'style' issues.

define(AC_CHECK_DEFINE,[dnl
  AC_CACHE_CHECK(for $1 in $2, ac_cv_define_$1,
    AC_EGREP_CPP([YES_IS_DEFINED], [
#include <$2>
#ifdef $1
YES_IS_DEFINED
#endif
    ], ac_cv_define_$1=yes, ac_cv_define_$1=no)
  )
  if test "$ac_cv_define_$1" = "yes" ; then
    AC_DEFINE([HAVE_$1],[],[Added by AC_CHECK_DEFINE])
  fi
])dnl
AC_DEFINE([HAVE_$1],[],[Added by AC_CHECK_DEFINE])