Add some more graphics feature and limit queries (resolves issue #1234).

love.graphics.getSupported():
 - Added “fullnpot” field, is true everywhere except on some older mobile devices. If false, mipmapping and wrap modes other than “clamp” can’t be used on non-power-of-two sized textures.
 - Added “pixelshaderhighp” field, is true everywhere except some older mobile devices. If false, “highp” precision can’t be used in pixel shaders and love will default to “mediump” instead.

love.graphics.getSystemLimits():
- Added “anisotropy” field, gets the maximum amount of anisotropy you can specify in Texture:setFilter. love will clamp anisotropy arguments greater than this value.

--HG--
branch : minor

src/modules/graphics/Graphics.cpp

@@ -258,6 +258,8 @@ StringMap<Graphics::Feature, Graphics::FEATURE_MAX_ENUM>::Entry Graphics::featur
 	{ "multicanvasformats", FEATURE_MULTI_CANVAS_FORMATS },
 	{ "clampzero", FEATURE_CLAMP_ZERO },
 	{ "lighten", FEATURE_LIGHTEN },
+	{ "fullnpot", FEATURE_FULL_NPOT },
+	{ "pixelshaderhighp", FEATURE_PIXEL_SHADER_HIGHP },
 };
 
 StringMap<Graphics::Feature, Graphics::FEATURE_MAX_ENUM> Graphics::features(Graphics::featureEntries, sizeof(Graphics::featureEntries));
@@ -268,6 +270,7 @@ StringMap<Graphics::SystemLimit, Graphics::LIMIT_MAX_ENUM>::Entry Graphics::syst
 	{ "texturesize", LIMIT_TEXTURE_SIZE },
 	{ "multicanvas", LIMIT_MULTI_CANVAS },
 	{ "canvasmsaa",  LIMIT_CANVAS_MSAA  },
+	{ "anisotropy",  LIMIT_ANISOTROPY   },
 };
 
 StringMap<Graphics::SystemLimit, Graphics::LIMIT_MAX_ENUM> Graphics::systemLimits(Graphics::systemLimitEntries, sizeof(Graphics::systemLimitEntries));