[Bug c/54823] string literal characters not constant

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54823

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-10-05 11:34:09 UTC ---
6.7.2.2 "The expression that defines the value of an enumeration constant shall
be an integer constant expression that has a value representable as an int."

See 6.6 for the valid forms of integer constant expressions.