Remove Meson build system

Less maintenance overhead that way,
given that make/CMake now also do library versioning.

meson.build

@@ -1,15 +0,0 @@
-project('raylib', 'c', version:	'1.8.0',
-		license: 'zlib',
-		meson_version: '>= 0.39.1',
-		default_options : 'c_std=gnu99')
-
-cc = meson.get_compiler('c')
-
-glfw_dep = dependency('glfw3', version : '>=3.2')
-gl_dep = dependency('gl')
-openal_dep = dependency('openal')
-x11_dep = dependency('x11')
-m_dep = cc.find_library('m', required : false)
-
-subdir('src')
-