Support for xorg-server 1.16

Hello,

This is an attempt to play with libglvnd on fedora 20/21 with RPM Fusion packaged drivers. Currently I cannot replace mesa-libGL on optimus device, probably because fedora mesa is built with tls support enabled This may explain issue like this: (EE) AIGLX error: dlopen of /usr/lib64/dri/i965_dri.so failed (/usr/lib64/dri/i965_dri.so: undefined symbol: glapi_tls (EE) AIGLX: reverting to software rendering (EE) GLX: could not load software renderer (II) GLX: no usable GL providers found for screen 0

v2: Test features with ABI_VIDEODRV_VERSION only use XVENDORNAME if defined.