In C++, set the type of each of the enumerators in an enumeration to

the type of the enumeration once the enumeration has been defined.

Fix the overloading test-case to properly create enums that promote
the way we want them to.

Implement C++0x promotions from enumeration types to long
long/unsigned long long. We're using these promotions in Carbon.h
(since long long is a common extension).

Fixes PR clang/2954: http://llvm.org/bugs/show_bug.cgi?id=2954

llvm-svn: 60917