- Changed the .NET 4 WeakReference<T> to better match the new WeakReference<T> type in .NET 4.5.

- Changed WeakValueDictionary because it derives from WeakReference<T>, but .NET 4.5 WeakReference is sealed.
- Renamed Theraot.Core.NET35.dll back to Theraot.Core.dll to avoid a mysterious error.
Merge branch 'master' of https://github.com/qwertie/Loyc

Conflicts:
	Src/Loyc.Essentials/G.cs
	Src/Loyc.Essentials/Loyc.Essentials.csproj
	Src/Loyc.Utilities/Loyc.Utilities.csproj