a68: allow joined list of revelations in access clauses

a68: allow joined list of revelations in access clauses

This commit adds support for having a joined list of revelations in
access clauses, like in:

  access Module18a,
         Module18b,
         Module18c
  begin assert (foo = 10);
        assert (bar = 20);
        assert (baz = 30)
  end

Signed-off-by: Jose E. Marchesi <jemarch@gnu.org>
gcc/algol68/ChangeLog

	* a68-parser-bottom-up.cc (reduce_enclosed_clauses): Reduce joined
	list of revelations.
	* a68-low-clauses.cc (a68_lower_revelation_ludes): New function.
	(a68_lower_access_clause): Use a68_lower_revelation_ludes.

gcc/testsuite/ChangeLog

	* algol68/compile/modules/module10.a68: New test.
	* algol68/execute/modules/program-18.a68: Likewise.
	* algol68/execute/modules/module18c.a68: Likewise.
	* algol68/execute/modules/module18b.a68: Likewise.
	* algol68/execute/modules/module18a.a68: Likewise.
	* algol68/compile/modules/program-11.a68: Likewise.
	* algol68/compile/modules/program-10.a68: Likewise.
	* algol68/compile/modules/module12.a68: Likewise.
	* algol68/compile/modules/module11.a68: Likewise.