[patch, libfortran] Fix matmul result zeroing for empty arguments

[Thomas Koenig]

Hello world,

the attached patch moves the zeroing of the result variable before the
early return. This is done so that the result for zero-sized arguments
is still valid.

The bug was only in the library version, but I have also added a test
case for the inline version to make sure the bug does not suddenly
appear there.

OK for trunk?

Regards

	Thomas

2017-06-05  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/80975
	* m4/matmul_internal.m4:  Move zeroing before early return.
	* generated/matmul_c10.c: Regenerated.
         * generated/matmul_c16.c: Regenerated.
         * generated/matmul_c4.c: Regenerated.
         * generated/matmul_c8.c: Regenerated.
         * generated/matmul_i1.c: Regenerated.
         * generated/matmul_i16.c: Regenerated.
         * generated/matmul_i2.c: Regenerated.
         * generated/matmul_i4.c: Regenerated.
         * generated/matmul_i8.c: Regenerated.
         * generated/matmul_r10.c: Regenerated.
         * generated/matmul_r16.c: Regenerated.
         * generated/matmul_r4.c: Regenerated.
         * generated/matmul_r8.c: Regenerated.
         * generated/matmulavx128_c10.c: Regenerated.
         * generated/matmulavx128_c16.c: Regenerated.
         * generated/matmulavx128_c4.c: Regenerated.
         * generated/matmulavx128_c8.c: Regenerated.
         * generated/matmulavx128_i1.c: Regenerated.
         * generated/matmulavx128_i16.c: Regenerated.
         * generated/matmulavx128_i2.c: Regenerated.
         * generated/matmulavx128_i4.c: Regenerated.
         * generated/matmulavx128_i8.c: Regenerated.
         * generated/matmulavx128_r10.c: Regenerated.
         * generated/matmulavx128_r16.c: Regenerated.
         * generated/matmulavx128_r4.c: Regenerated.
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