While building drivers against xserver-1.16 compiled on a glibc-2.20 system, I seem to be getting a lot of errors like these:

In file included from /usr/include/string.h:634:0,
                 from /usr/include/xorg/os.h:53,
                 from /usr/include/xorg/misc.h:115,
                 from /usr/include/xorg/xf86str.h:37,
                 from /usr/include/xorg/xf86Xinput.h:54,
                 from synproto.h:36,
                 from synproto.c:26:
/usr/include/xorg/os.h:579:1: error: expected identifier or '(' before '__extension__'
 strndup(const char *str, size_t n);

Looks like xserver is redefining stuff that's now part of glibc-2.20. I am not sure what. I have built two drivers, xf86-input-vmmouse and xf86-input-synaptics and both fail to build with same error. I suppose there would be more.