site: add xorg_cv_malloc0_returns_null
util-macros 1.18 will look in the autoconf cache for this value so instead of
using overrides in xorg-lib-common, use the per-libc site cache.
Alert readers may notice that the site file claims that glibc returns NULL from
malloc(), when the previous change (
e628c8aba0189de30de2833882b9999ff3b6547a)
claimed that it didn't. The previous change was incorrect, whilst malloc(0)
returns a valid pointer, realloc(p,0) does in fact return NULL, so the Xlib
wrapper functions are needed.
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
