Fix PR 32336 (error message for matmul)

[FX Coudert]

> Regtesting on i686-pc-linux-gnu as I write this.
>
> OK for trunk if this passes?
>
> 	Thomas
>
> 2007-07-09  Thomas Koenig  <tkoenig@gcc.gnu.org>
>
> 	PR libfortran/32336
> 	* m4/matmul.m4:  When the dimension of b is incorrect,
> 	raise a runtime error instead of a failed assertion.
> 	* generated/matmul_i1.c:  Regenerated.
> 	* generated/matmul_i2.c:  Regenerated.
> 	* generated/matmul_i4.c:  Regenerated.
> 	* generated/matmul_i8.c:  Regenerated.
> 	* generated/matmul_i16.c:  Regenerated.
> 	* generated/matmul_r4.c:  Regenerated.
> 	* generated/matmul_r8.c:  Regenerated.
> 	* generated/matmul_r10.c:  Regenerated.
> 	* generated/matmul_r16.c:  Regenerated.
>
> 2007-07-09  Thomas Koenig  <tkoenig@gcc.gnu.org>
>
> 	PR libfortran/32336
> 	* gfortran.dg/matmul_5.f90:  New test case.

OK if it regtests.