Previously the configure script would silently disable the use of
accelerated cairo in the clients if cairo-gl could not be found (or
cairo-glesv2 if that was requested.) Conversely the use of cairo-gl
would be automatically enabled if it was found with no way to disable
that feature

This change adds --with-cairo which takes one of "image", "gl" or
"glesv2" (defaulting to "image"). If "gl" or "glesv2" is specified
cairo-egl is checked for as well as the specified renderer. If the check
fails then the configure process errors out.