GenexEval: Fix evaluation of INCLUDE_DIRECTORIES target property.

This property should come from the content of the property itself,
plus the INTERFACE_INCLUDE_DIRECTORIES of the link *implementation*.

In contrast, when the INTERFACE_INCLUDE_DIRECTORIES is evaluated for
a target, the INTERFACE_INCLUDE_DIRECTORIES of the link *interface*
is used.

Similar logic applies for the COMPILE_DEFINITIONS target properties.

If the propertyName is already an INTERFACE_ variant of the property,
ie, the expression is similar to

 $<TARGET_PROPERTY:foo,INTERFACE_INCLUDE_DIRECTORIES>

then the INTERFACE_INCLUDE_DIRECTORIES of the link *interface* of foo
is used.

However, if the propertyName is not an INTERFACE_ variant, and the
interfacePropertyName is, ie, the expression is similar to:

 $<TARGET_PROPERTY:foo,INCLUDE_DIRECTORIES>

then the INTERFACE_INCLUDE_DIRECTORIES of the link *implementation*
of foo is used.