bound simplification refactoring

bound simplification refactoring

gcc/fortran/
	* simplify.c (simplify_bound_dim): Don't check for emptyness
	in the case of cobound simplification.  Factor lower/upper
	bound differenciation before the actual simplification.
	(simplify_bound): Remove assumed shape specific simplification.
	Don't give up early for the lbound of an assumed shape.
gcc/testsuite/
	* gfortran.dg/bound_simplification_5.f90: New.

From-SVN: r222979