[Committed] Update Fortran MATMUL documentation

[Steve Kargl]

I've committed the following patch after a 'make pdf'
to verify that the change is formatted correctly.  The
patch updates the documentation for Fortran's MATMUL
intrinsic.

2018-02-23  Steven G. Kargl  <kargl@gcc.gnu.org>

	* intrinsic.texi: Arguments to MATMUL cannot both be rank one.

Index: intrinsic.texi
===================================================================
--- intrinsic.texi	(revision 257951)
+++ intrinsic.texi	(working copy)
@@ -9870,6 +9870,7 @@ one or two.
 type; otherwise, an array of @code{LOGICAL} type. The rank shall be one
 or two, and the first (or only) dimension of @var{MATRIX_B} shall be
 equal to the last (or only) dimension of @var{MATRIX_A}.
+@var{MATRIX_A} and @var{MATRIX_B} shall not both be rank one arrays.
 @end multitable
 
 @item @emph{Return value}:

-- 
Steve