The outer glfwUpdateGamepadMappings function is now bypassed when
parsing the default gamepad mappings. The data in mappings.h does not
contain any comments or line breaks. Also this is done before joystick
support has been initialized, so there is no need to look for matching
devices.
Finally, the array of default mappings is pre-allocated. This has no
measurable performance impact but does generate a lot of calls, which
won't be nice for a user provided custom allocator to deal with.
The SDL2 2.0.5+ controller GUID 03000000790000000600000000000000 matches
many devices with different layouts and element counts but with the same
chipset. This issue is still being resolved upstream. In the meantime
this removes those mappings from GLFW to avoid confusion and errors.
SDL upstream issue: https://bugzilla.libsdl.org/show_bug.cgi?id=4545
Related to #1583.
