[fortran] ICE in gfc_validate_kind(): Got bad kind [PR93580]

Caused by using invalid part_refs in kind specifications,
e.g. %re or %im on non-complex expressions and %len on
non character expressions.

Check whether %re, %im and %len are valid when checking
kind specification.

The original patch from Steven G. Kargl  <kargl@gcc.gnu.org> only
checked for %re and %im.

gcc/fortran/ChangeLog:

	PR fortran/93580
	* primary.c (gfc_match_varspec): If the symbol following %
	is re or im and the primary expression type is not BT_COMPLEX
	issue an error. If the symbol is len and the primary
	expression type is not BT_CHARACTER is an error.

gcc/testsuite/ChangeLog:

	PR fortran/93580
	* gfortran.dg/dg/pr93580.f90: New test.