c++: unsigned int32_t enum promotion [PR102804]

There's been an extension for a long time to allow applying 'unsigned' to an
int typedef, but that was confusing the integer promotion code.  Fixed by
forgetting about the typedef in that case.

I'm going to make this an unconditional pedwarn in stage 1.

	PR c++/102804

gcc/cp/ChangeLog:

	* decl.cc (grokdeclarator): Drop typedef used with 'unsigned'.

gcc/testsuite/ChangeLog:

	* g++.dg/ext/unsigned-typedef1.C: New test.