Added draw functions:
ImageClearBackground()
ImageDrawPixel()
ImageDrawLineEx()
ImageDrawCircle()

This was working in 2.6 but no longer does in current git tree.
It appears touch position is only tracked on
AMOTION_EVENT_ACTION_[DOWN|UP], which only registers the initial touch
on the screen. Subsequent movement is not tracked into CORE.

Touch position and the Gesture System appears to be updated twice in
AndroidInputCallback in what looks like perhaps a copy paste error (code
is identical) with the exception of tracking AMOTION_EVENT_ACTION_UP in
the 2nd copy of the code (but this is not necessary to track).

If you need to track the first touch or release touch position, you can
do so with checking IsMouseButton[Pressed|Released] on the same frame.

This patch makes it so the touch position is always updated, and merges the
duplicated code into 1 singular code path.

NOTE: Two libraries still use custom allocators: glfw and stb_vorbis

NOTE: This functionality has an important issue, line space is fixed to 1.5 font.baseSize pixels, depending on the font and how it has been generated that spacing could be too wide or too narrow...

In `InitGraphicsDevice(...)`, the Android section has a screen security check
like other platforms- but CORE.display.width, CORE.display.height are
not set yet, so the security check sets it to 0. So ensure we query the
device's screen width and height before the screen size security check.

This also gives you the ability to run a proper full-screen application
on Android without any scaling and guess work on the target device by
setting screen width and height to 0 in `InitWindow(...)` and using
`GetScreen[Width|Height]()` to get the actual values.

Improved file access checks

Very weird... lately icons are not properly displayed on browser!

After several reviews, now it seems everything works as expected.

* Update raymath.h

Added Vector2Rotate Function.

* Update raymath.h

IsMouseButtonDown() does not process touch state down properly, state is reseted every frame...

Guarantee string is zero-terminated

Use new file I/O ABI

Use new file I/O ABI

Using new file I/O ABI

Using new file I/O ABI

Using new file I/O ABI

Using new file I/O ABI

Renamed functions for consistency:

 - StorageLoadValue() > LoadStorageValue()
 - StorageSaveValue() > SaveStorageValue()