[PATCH] Tame a few enum size tests when using -fshort-enums on ARM.

[Eric Fiselier]

The patch you have now looks good but I think a more universal solution might be better since these tests will fail whenever -f-short-enums is used. Something like:
```
    test_make_signed<const Enum, std::conditional<sizeof(Enum) == sizeof(int), const int, const signed char>::type>()
```
Out of curiosity how are you getting the -fshort-enums flag into lit to test?

http://reviews.llvm.org/D4869