Updated version to `rlgl 4.2`

* Update raylib.h

* CheckCollisionPointPolygon()

* typo

I want to note this is a special symbol exported

Reasons to NOT define `_GNU_SOURCE`:

 - access to lots of nonstandard GNU/Linux extension functions
 - access to traditional functions which were omitted from the POSIX standard (often for good reason, such as being replaced with better alternatives, or being tied to particular legacy implementations)
 - access to low-level functions that cannot be portable, but that you sometimes need for implementing system utilities like mount, ifconfig, etc.
 - broken behavior for lots of POSIX-specified functions, where the GNU folks disagreed with the standards committee on how the functions should behave and decided to do their own thing.

WARNING: This could be a BREAKING CHANGE for some platforms! I'm afraid something could be wrong on `rglfw.c` module.

To be able to compile on Windows I had to modify `glfw/src/platform.c` line 74. I couldn't manage to compile without that change, help is welcome!

This linkage is only required for arm 32bit but I don't know how to detect that specific architecture in the Makefile...

* Win32: resolve some symbols re-definition of windows.h in glfw3native.h

This reflects GLFW's fix: https://github.com/glfw/glfw/issues/1348

This enables to build with a external GLFW containing the
following fix:

* 05f6c13d11

Currently, glfw3native.h of the internal GLFW is customized at
2feea87b61

This fix is compatible with the current customized glfw3native.h.

This fix enables us to update it to the latest and remove the
customization.

* Win32: remove unneeded typedef

When file extension is longer or equal length compared to buffer holding lowercased string, strncpy does not null terminate the string.
Increased buffer size by 1 to ensure it will always be null-terminated, so that following strcmp does not read out of buffer bounds.

This truncation causes text that spans the zero coord boundary to round differently left or zero vs. right of zero, in turn causing letters to appear squished together. If you actually need the position to be an integer, you should instead `floorf()` the float, rather than doing an integer truncation, but I don't see any reason to convert it to an integer in the first place. Everything else in the equation is a float.

GetMusicTimePlayed() was calculated using buffered frames, not played frames.
For example: calling LoadMusicStream->UpdateMusicStream->GetMusicTimePlayed would return non-zero value, even though no music was playing.

Moved to own repo: https://github.com/raylib-extras/rmem

Tested with latest emscripten 3.1.18