updating libgfortran/generated/

[Tim Prince]

If memory hasn't failed me, I used to test modifications to matmul by 
editing matmul.m4.  Then, since my build is configured with 
--enable-maintainer-mode, running make in libgfortran would update the 
corresponding files.  Today, I can't figure out how to update matmul*.c.
matmul performance on current production CPUs seems to be limited by 
cahe to register transfers, so I wanted to test some unroll-and-jam 
modifications.