free() and NULL at the end.

It would be good to have a way to continue execution even when loading a stream didn't work.
 Free music and set it to NULL in case something went wrong, so that users can check for it.

Still a work in progress but it already works...
Current riqm API could be simplified...

as well as -DUSE_EXTERNAL_GLFW.

Nips issues like #584 in the bud.

Examples can be compiled for web with no code change at all! Usually
examples need to be refactored for web... using emscripten code
interpreter (emterpreter), it can manage synchronous while() loops
internally... as a downside, execution is very slow...

This change allows rlgl.h usage as independent single-file header-only module... still some tweaks required, like removing GLAD dependency... required extensions could be manually loaded!

Also removed shader_distortion.h, embedded in rlgl.h

Corrects issue with audio on RPI

pkg-config --libs --static raylib and pkg-config --libs raylib
should give the same result if there is no shared raylib installed.

Vector4 -> Quaternion
Texture2D -> Texture
RenderTexture2D -> RenderTexture
Camera3D -> Camera
SpriteFont -> Font

Fixes: #568

Note for me: Replace All is NOT your friend...

Library consistency rename... yes, I know, it breaks the API...

Joystick support is not implemented just yet, not difficult but it
requires some work...

if (${PLATFORM} MATCHES "Desktop")
  target_link_libraries(${RAYLIB}_shared glfw ${GLFW_LIBRARIES})

was never true because PLATFORM STREQUAL "PLATFORM_DESKTOP"...

This fixes #551 and makes the changes suggested in #552 (commited as 965cc8ab)
unnecessary.

Fixes: e1e036a6 ("Disable glfw only when it is not found and not external", #558)

This function was added in text module as GenImageFontAtlas()

Rotate a Vector3 by a Quaternion