This is just cosmetic. No change in function.

… syntax

Also added infrastructure for comparing two patches to the test
framework.

This also means that ptest now requires libm.

…y leaks

This also uses valgrind. Note that we still have plenty of memory
leaks, so the regression tests won't pass with "make leak".

We never access some identifiers, so the only effect of explicitly
free(3)ing them is that this creates a reference which in turn prevents
lemon from generating code that does the freeing automatically.