OPENGL: Support GLES2 contexts.

configure

@@ -945,6 +945,7 @@ Optional Features:
                                             any for runtime detection
                                             gl for forcing OpenGL
                                             gles for forcing OpenGL ES
+                                            gles2 for forcing OpenGL ES 2
                            WARNING: only specify this manually if you know what
                            you are doing!
 
@@ -2659,9 +2660,11 @@ if test -n "$_host"; then
 			# since SDL2 manages dispmanx/GLES2 very well internally.
 			# SDL1 is bit-rotten on this platform.
 			_sdlconfig=sdl2-config
-			# OpenGL(ES) support is mature enough as to be the best option on
+			# OpenGL ES support is mature enough as to be the best option on
 			# the Raspberry Pi, so it's enabled by default.
-			_opengl_mode=gles
+			# The Raspberry Pi always supports OpenGL ES 2.0 contexts, thus we
+			# take advantage of those.
+			_opengl_mode=gles2
 			;;
 		dreamcast)
 			append_var DEFINES "-DDISABLE_DEFAULT_SAVEFILEMANAGER"
@@ -4224,6 +4227,11 @@ case $_opengl_mode in
 		echo "yes (OpenGL ES)"
 		add_line_to_config_h "#define USE_GLES_MODE 1"
 		;;
+
+	gles2)
+		echo "yes (OpenGL ES 2)"
+		add_line_to_config_h "#define USE_GLES_MODE 2"
+		;;
 esac
 
 define_in_config_if_yes "$_opengl" "USE_OPENGL"