Required by ProcessGestureEvent()

Mouse input is interpreted as touches to allow mouse gestures
detection... and get an unified inputs system for all platforms!

- Fixed gestures hold detection.
- Improved hold state detection for little touch position increments
(sensitivity).

Removed GLEW external dependency, now it works with GLAD
Kept GLEW path, just in case... detected weird behaviour when testing
with gDEBugger

This reverts commit 423a45ac85.

Added support for single header implementation and also inline functions
support

- Added simple ray-sphere collision detection.
- Added extra function with extended parameters to obtain collision
point vector.
- Fixed bounding box calculations init values (were causing compiling
errors).

look over for errors

Reviewed vertex type variables

- Added function WorldToScreen(...).
- Added world to screen example.
- Review GetMouseRay() comment.
- Removed deprecated lighting functions from raylib header.

Simplified for the user (more intuitive and clear)
Removed lighting module dependency

... transparent elements

It seems that now works. Tested all free camera features with some
directions and positions and no unexpected behaviours detected. I don't
know if those lines are really indispensable.

- Added CheckCollisionRayBox() function.
- Updated and improved core 3d picking example (currently working as
expected).

- Fixed GetMouseRay() function.
- rlglUnproject() unused.

- Fixed Android locking screen bug. OnDestroy() was called when locking
screen.
- Power button input must be handled by OS.
- AndroidManifest.xml is affected by configChanges="screenSize".
- Updated library header for android template.

- Added functions for detect when pressed, during down and when
released.
- Added defines for back, menu, volume up and down button numbers.

Two new functions added to save/load values as binary data:
- StorageSaveValue()
- StorageLoadValue()

- Improved physics calculations.
- Added AddForceAtPosition function (added to all enabled rigidbodies).
- Updated raylib header.

Corrected Android processing for some inputs (BACK button, VOLUME
buttons)
Redesigned Gestures system (some work still required)
SetEnabledGestures() - Only support desired gestures (requires some
review)

Added LoadBMFont() to load AngelCode fonts (.fnt)
Implemented LoadTTF() to load .ttf fonts (crappy packaging)