Generate the contents of OpCodeNames.c.

This was another one that was pretty easy to add to opcode-gen. I did
end up tweaking opcode-gen to make it obvious that the two forms of
name are different by more than just upper vs. lower case, especially
because I duplicated the original distinction of the optimized opcodes
having extra prefix characters in their human-oriented names but not
in the names when used as programming constants.

Change-Id: I5062442540d26318914964bd2722cc32380b19ca