fortran: Object types should be declared before use in NAMELIST.

fortran: Object types should be declared before use in NAMELIST.

gcc/fortran/ChangeLog:

	PR fortran/98686
	* match.c (gfc_match_namelist): If BT_UNKNOWN, check for
	IMPLICIT NONE and and issue an error, otherwise set the type
	to its IMPLICIT type so that any subsequent use of objects will
	will confirm their types.

gcc/testsuite/ChangeLog:

	PR fortran/98686
	* gfortran.dg/namelist_4.f90: Modify.
	* gfortran.dg/namelist_98.f90: New test.