The overloaded log() is a unary operator, so don't pass additional
arguments.Fix blog() so the cases $x->blog() and $x->blog(undef) work correctly. An
undefined base means that blog() should use base e (Euler's number).Both CORE::log() and other mathematical software returns inf for log(inf),
so we do the same.Add tests for log() as well as templates for future tests of the other
overloadable functions.Improve descriptions of a few tests.