mapi: add GetInteger64vEXT with EXT_disjoint_timer_query

From EXT_disjoint_timer_query spec:

"Interaction: This extension adds GetInteger64vEXT if OpenGL ES 3.0 is not supported"

See https://github.com/KhronosGroup/OpenGL-Registry/issues/326.

Closes: #2090 (closed) Signed-off-by: Tapani Pälli tapani.palli@intel.com