RFR: 8071291 - Compiler crashes trying to cast UnionType to IntersectionClassType

[Rob McKenna]

Hi folks,

Looking to backport this change to 8. There is a slight difference in 
the fix between 8 & 9 in that makeIntersectionType(Type bound1, Type 
bound2) (née makeCompoundType(Type bound1, Type bound2)) is still in use 
in 8.

http://cr.openjdk.java.net/~robm/8071291/webrev/

	-Rob