glapi/check_table: Remove 'extern "C"' block

glapi/check_table: Remove 'extern "C"' block

Using 'extern "C"' around includes is always incorrect, as the header may
contain C++ symbols (as it does in this case), which means it cannot use
C linkage. In this case the header has a template in it, which obviously
cannot be linked with C linkage rules.

Fixes: a29ad2b421b75a1727b ("mesa/tests: Add tests for the generated dispatch table")
Signed-off-by: Dylan Baker <dylan.c.baker@intel.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>