c++/6828: g++3 makes wrong mangled name for template cast operator

[Kriang Lerdsuwanakij]

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6828

The reason the fix didn't get into GCC 3.1.1 is that the
changed name mangling break ABI compatibility.  But the fix
will appear in the soon to be released GCC 3.2.  GCC 3.2 is
GCC 3.1.1 with extra bug fixes that provide no backward
binary compatibility.