Now floating point is either on or off. This simplifies the use of 16bit
vs float.

updateAudioContext is almost done

Ease of use considered in api and channels are more convenient as
unsigned char type.

Removed BeginDrawingEx()
Added Begin2dMode() and End2dMode()

Hiding the struct from user should protect from accidentally modifying
the mix channel. This could cause serious errors down the road.

Look over changes and give feedback please.

Boolean errors

... easy code porting, transalating them to touches and gestures
internally.

Removed function SetCustomCursor(), it can be managed by the user.

I decided it is redundant and could be confusing (when mixed with 3D
drawing). It's not KISS.

Now it's possible to render to texture, old postprocessing system will
be removed on next raylib version.

Finally, physics update is handled in main thread using steps to get
accuracy in collisions detection instead of moving it to a new thread.

Examples are finished as simple and clear as I could. Finally, physac
module is MORE simpler than in the first version, calculation everything
by the same way for both types of physic objects.

I tryed to add rotated physics a couple of times but I didn't get
anything good to get a base to improve it. Maybe for the next version...

No bugs or strange behaviours found during testing.

Now it works ok also in RaspberryPi

Requires Shader access functions review

physac modules is being redesigned. Physics base behaviour is done and
it is composed by three steps: apply physics, resolve collisions and fix
overlapping.

A basic example is currently in progress. The next steps are try to add
torque and unoriented physic collisions and implement physics basic
functions to add forces. Rigidbody grounding state is automatically
calculated and has a perfect result. Rigidbodies interacts well with
each others.

To achieve physics accuracy, UpdatePhysics() is called a number of times
per frame. In a future, it should be changed to another thread and call
it without any target frame restriction.

Basic physics example has been redone (not finished) using the new
module functions. Forces examples will be redone so I removed it from
branch.

Specially useful on default font scaling

- Removed DrawQuad() function
- DrawBillboard() uses DrawBillboardRec()
- DrawPlane() uses RL_TRIANGLES
- DrawRectangleV() uses RL_TRIANGLES, that way, [shapes] module uses
only TRIANGLES buffers.

Using normalized [0..1] input points

A deeper revision required, not clear enough for the user
Key: Create a PhysicObjects pool

sin(), cos() functions cached and replaced by float c99 versions sinf(),
cos()

...and improved mouse gestures support
Some testing still required...