if the nullptr check is useful for some *non-compliant* compiler, user may still ignore this rule.
oclint provides a set of rules, user may pick the ones he wants.
As a note, [cppcheck](http://cppcheck.sourceforge.net/) also reports that the check for nullptr for delete is useless.

but as I said, `delete p` with `p == nullptr` should be valid, else "delete" or "compiler" is not compliant.

I'm open to better name.