Add support for DrawShading
NSUnderlineStyle: don't define on MONOMAC

MonoMac's AppKit defines the full version of NSUnderlineStyle,
so don't conflict with it.
Merge pull request #41 from kjpou1/master

Add support for DrawShading
Introduce a SmartLink value to the LinkWith attribute.

If this value is true, ForceLoad will be ignored when we can determine
that it will not cause any problems.
Use ToUpperInvariant instead of culture version