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.
(cherry picked from commit 201400b974)
This fixes gamepad mappings being included in GLFW binaries that would
then never use them because they were for a different platform.
(cherry picked from commit 0c90e1a33f)
