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

Added: data to CharInfo struct
Added: LoadFontData()
Added: GenImageFontAtlas()
Removed: LoadFontEx()
Removed: LoadTTF() [internal]
Some code tweaks

- GetImageData()
- GetImageDataNormalized()

...by emscripten glfw javascript implementation

Reviewed: GetImageData()
Reviewed: ImageFormat()

ImageDraw() code tweak