Fix stencil clear

Some drivers (especially on Android) will obey the stencil test when clearing the stencil buffer (the specs says it shouldn't). This workaround ensure that the stencil buffer will properly be cleared.
Added missing semicolon
Removing assert Pow2 from Texture.GetPitch. It is not appropriate to have this assert in the base Texture.cs file because it is platform specific whether or not this is actually a valid constraint and area already doing their own dimension validation.
Merge branch 'develop' of https://github.com/SickheadGames/MonoGame into develop
Merge pull request #2482 from prollin/patch-1

Fix stencil clear
Now using FreeImage to import Textures on Windows.
Added missing Microsoft.Xna.Framework.Graphics exceptions.
Changed SerializableAttribute to DataContract so it can compile on all platforms.
Updated TextureImporter with all of the file types that FreeImage supports.
Feeble attempt at formatting the massive amount of RAW image formats.
Merge pull request #2486 from SickheadGames/DeviceLostException

Added Missing Microsoft.Xna.Framework.Graphics Exceptions
Merge pull request #2485 from SickheadGames/FreeImageSupport

FreeImage TextureImporter Support