WMF/EMF: Unify all definitions of enums and flags between WMF and EMF.

This means that there will no longer be some value doubly defined,
which created problems when another file used both WMF and EMF.

* Move all WMF enums that were previously defined in EmfEnums.h to
WmfEnums.h
* Remove those that were doubly defined from EmfEnums.h and include
WmfEnums.h instead.
* Create a somewhat ugly hack for those enums that were extended from
WMF to EMF.