re PR fortran/15620 (Statement functions and optimization cause IC)

re PR fortran/15620 (Statement functions and optimization cause IC)

	PR fortran/15620
	* trans-decl.c (gfc_shadow_sym, gfc_restore_sym): New functions.
	* trans-expr.c (gfc_trans_string_copy): New function.
	(gfc_conv_statement_function): Use them.  Create temp vars.  Enforce
	character lengths.
	(gfc_conv_string_parameter): Use gfc_trans_string_copy.
	* trans-stmt.c (gfc_trans_forall_1): Use gfc_{shadow,restore}_sym.
	* trans.h (struct gfc_saved_var): Define.
	(gfc_shadow_sym, gfc_restore_sym): Add prototypes.
testsuite/
	* gfortran.fortran-torture/execute/st_function_1.f90: New test.
	* gfortran.fortran-torture/execute/st_function_2.f90: New test.

From-SVN: r82452