Modification for MacOSX mouse wheel support.  This fixes Open Issue https://github.com/mono/MonoGame/issues/2276.
Merge pull request #2452 from mono/xamarin

Modification for MacOSX mouse wheel support.  This fixes Open Issue http...
Remove VertexElementDeclaration fixes #2304
Fix a few more minor warnings. (Shader change from @flibitijibibo)
Merge pull request #2453 from danzel/fix-2304

Remove VertexElementDeclaration
Merge pull request #2454 from danzel/more-warnings

Fix a few more minor warnings
Merge back from develop