Devel: Rearrange and enable tests for coccinelle.

First, split the input C file and expected output semantic patch into
separate files. It's just easier for me to tell what's going on that
way.

Second, rename _testrunner.sh to testrunner.sh and make other changes to
it. Adapt to the input and output being split apart. Protect the rm
against the temp directory somehow no longer existing (so it doesn't end
up evaluating to "rm /*". Don't close stdin. Just use /bin/sh
directly.

Third, add a cocci-test target to GNUmakefile that will iterate over all
the devel/coccinelle/test/*.c files. In the best case, $? will be 0.