Support building for Wayland

[Peter0x44]

Since GLFW 3.4, there are no longer separate builds of "glfw-wayland" and "glfw-x11". There is no need to pick what you want to support when building GLFW,

Currently, adding a define of _GLFW_WAYLAND results in this error:

In file included from src/rglfw.c:107:
src/external/glfw/src/wl_init.c:45:10: fatal error: xdg-shell-client-protocol.h: No such file or directory
   45 | #include "xdg-shell-client-protocol.h"
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.

I believe this header is generated by invoking some shell commands (wayland-scanner and wl-generate), and there are several others.
https://github.com/raysan5/raylib/blob/9cf408f77c58828fd1019d5cd35c6b8c5139c8dc/src/Makefile#L414-L435

This is the part of raylib's makefile responsible for creating them.

I opened this issue mostly for myself.