opt: incidental comment and whitespace repair

opt: incidental comment and whitespace repair

This comment occurred in a couple of places:

 /* Set an integer value, various forms.  Sets to 1 on arg == NULL. */

One instance was clearly spurious, while the other was misleading.

Another resolution to this mismatch would be to add
"if (arg == NULL){*l = 1; return NULL}" somewhere, but I suspect
it may have been left out/removed because someone thought better.