Add a matmul_02 test

[certik]

Fixes #2444.

[certik]

matmul_02 just does not want to run at the CI:

663/663 Test #646: matmul_02 .........................Subprocess aborted***Exception:   0.15 sec
Size (n x n): n = 96
Iter = 1
Size MB: 3.51562500000000000e-02
Fortran intrinsic matmul:
Time:  5.29800000000000409e-03
Clock cycles per element:
Theoretical performance peak: 6.25000000000000000e-02 cycles
Measured:                     1.91623263888889070e+01 cycles
Percent peak:                 3.26160815402038173e-01 %

matmul7:
Error: 1.64040939e+02
Time:  9.39100000000000351e-03
Clock cycles per element:
Theoretical performance peak: 6.25000000000000000e-02 cycles
Measured:                     3.39662905092592737e+01 cycles
Percent peak:                 1.84005963156213315e-01 %

matmul1:
Error: 8.02753830e+01
Time:  2.74599999999999844e-03
Clock cycles per element:
Theoretical performance peak: 6.25000000000000000e-02 cycles
Measured:                     9.93200231481480778e+00 cycles
Percent peak:                 6.29278951201748482e-01 %
free(): invalid next size (normal)

[certik]

I opened up #2792 for the missing part.