Moved PBR material loading to example, right decision?

Problems when compiling with VS2015
Probably DEBUG(...) macro is not the best naming...

...to avoid possible conflicting symbols

Namely:
- GenImageHorizontalV
- GenImageHorizontalH
- GenImageChecked
- GenImageWhiteNoise
- GenImageCellular

The gradient implementation may be a bit naive, for example it doesn't do any gamma correction.

If we compile with c99 without gnu extensions (gnu99) we need this
define, to have CLOCK_MONOTONIC and similar macros available

This should always be the number of the raylib release.
Especially when the new version is ABI incompatible the major version
should be bumped.

Using the library() function instead of shared_library() allows changing
of the library type via the default_library option.
This allows for easy change between static and dynamic library building.

Use 'meson --default-library=static builddir' to build as static, if no builddir yet exists.
Use 'mesonconf -Ddefault_library=static builddir' to change the type for
an existing builddir.

Some distributions build the programs with a specific set of CFLAGS.
Lets allow that by adding raylibs flags.

Issues when pausin musing and trying to resume (not resuming!)

Setup for a new amazing feature! ;)

Note that Android and Desktop versions of OpenAL Soft come from the same
sources, recompiled for every platform

Just waiting for a better future alternative (multiplatform)... OpenXR ?

Replaced by standaloane-toolchain based building, included in
src/Makefile