Use the local name instead of the original name in the check for name conflicts

Use the local name instead of the original name in the check for name conflicts
between a hosting program unit and use-associated symbols
in that program unit.

fortran/
	PR fortran/63744
	* module.c (check_for_ambiguous): Change argument type
	from gfc_symbol to gfc_symtree.  Check local (symtree) name
	instead of original (symbol) name.
	(read_module): Update caller.

testsuite/
	PR fortran/63744
	gfortran.dg/use_rename_8.f90: New.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@220515 138bc75d-0d04-0410-961f-82ee72b054a4