mesa: Add QueryBuffer to context

v2: Add check for desktop gl and ARB_query_buffer_object extension
    when returning QueryBuffer in get_buffer_target

Add QueryBuffer and initialise it to NullBufferObj
on start
mesa: Handle QUERY_BUFFER_BINDING in GetIntegerv

v2: Expose query buffer binding location
    only when extension is enabled
mesa: Handle QUERY_RESULT_NO_WAIT in GetQueryObject{ui64}v

v2: Remove c++ comment style

Just return and do nothing if query result is not yet available
mesa: Fix typos in function names in queryobj
mesa: Implement software fallback for ARB_query_buffer_object

v2: In v1 &q->Ready was passed into query_store_result
    which could cause segfault in memcpy.
    (q->Ready is bool of size 1, while size parameter could be 4 or 8)
    Now store result in local variable and pass pointer to it instead.
mesa: Enable GL_ARB_query_buffer_object for software drivers

v2: Only enable extension for software driver
doc: mark GL_ARB_query_buffer_object as done for swrast