Dear Fortranners,

when debugging the testcase, I noticed that a coarray declaration in
a COMMON statement wrongly set the dimension attribute instead of the
codimension.  As a consequence, subsequent checks that catch this
invalid situation would not trigger.

I see two possible solutions:

- in gfc_match_common, replace

	  /* Deal with an optional array specification after the
	     symbol name.  */
	  m = gfc_match_array_spec (&as, true, true);

  by

  m = gfc_match_array_spec (&as, true, false);

  which in turn would lead to a syntax error.  Interestingly, the Intel
  compiler also takes this route and gives a syntax error.

- check the resulting as->corank and emit an error as in the attached
  patch.

The attached patch regtests fine on x86_64-pc-linux-gnu.  OK for mainline?

Thanks,
Harald