change name variable

To support multiple keys (including function keys)

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

- Check if first character is the expected Space char (32)
- Check if characters are ordered in definition file (.fnt)

- 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...