a68: consolidate refs when lowering formulas

It is necessary to consolidate operands of both monadic and dyadic
formulas so that paremeters expecting references will get an address.

Signed-off-by: Jose E. Marchesi <jemarch@gnu.org>

gcc/algol68/ChangeLog

	* a68-low-units.cc (a68_lower_formula): Consolidate operands of
	formula before call.
	(a68_lower_monadic_formula): Likewise.

gcc/testsuite/ChangeLog

	* algol68/execute/formula-3.a68: New test.
	* algol68/execute/formula-4.a68: Likewise.
	* algol68/execute/formula-5.a68: Likewise.