Fix C++ canonicalization of hex literals

Currently names like "x::y::z<1>" and "x::y::z<0x01>" canonicalize to
different things.  I think it's nicer for them to be the same.
Differences between types can be done using suffixes like "ll" and "u"
-- it's not really possible to implement C++ rules in the
canoncalizer, because no gdbarch is available.  Possibly gdb should
even drop the type here and just represent all integers the same way
in names.

Approved-By: John Baldwin <jhb@FreeBSD.org>