Allow static/dynamic library building with meson

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.

src/meson.build

@@ -12,8 +12,10 @@ source_c = [
   'external/stb_vorbis.c',
 ]
 
-raylib = shared_library('raylib',
-                        source_c,
-                        dependencies : [ glfw_dep, gl_dep, openal_dep, m_dep, x11_dep],
-                        install : true)
+# 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
+raylib = library('raylib',
+                  source_c,
+                  dependencies : [ glfw_dep, gl_dep, openal_dep, m_dep, x11_dep],
+                  install : true)