PR fortran/18833
	PR fortran/20850
	* primary.c (match_varspec): If equiv_flag, don't look at sym's
	attributes, call gfc_match_array_ref up to twice and don't do any
	substring or component processing.
	* resolve.c (resolve_equivalence): Transform REF_ARRAY into
	REF_SUBSTRING or nothing if needed.  Check that substrings
	don't have zero length.

	* gfortran.dg/equiv_1.f90: New test.
	* gfortran.dg/equiv_2.f90: New test.
	* gfortran.fortran-torture/execute/equiv_2.f90: New test.
	* gfortran.fortran-torture/execute/equiv_3.f90: New test.
	* gfortran.fortran-torture/execute/equiv_4.f90: New test.

From-SVN: r102801