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/opengl/OpenGL.h

@@ -383,6 +383,7 @@ public:
 	void setTextureWrap(const graphics::Texture::Wrap &w);
 
 	bool isClampZeroTextureWrapSupported() const;
+	bool isPixelShaderHighpSupported() const;
 
 	/**
 	 * Returns the maximum supported width or height of a texture.
@@ -409,6 +410,12 @@ public:
 	 **/
 	float getMaxPointSize() const;
 
+	/**
+	 * Returns the maximum anisotropic filtering value that can be used for
+	 * Texture filtering.
+	 **/
+	float getMaxAnisotropy() const;
+
 
 	void updateTextureMemorySize(size_t oldsize, size_t newsize);
 
@@ -438,6 +445,7 @@ private:
 
 	bool contextInitialized;
 
+	bool pixelShaderHighpSupported;
 	float maxAnisotropy;
 	int maxTextureSize;
 	int maxRenderTargets;