PN_FNUMBER=>PN_FINTEGER, add seperate int+dbl methods

IS_NUM is a misnomer. Number is Integer or Double.
Provide seperate methods for future specialized _ii and _dd ops,
esp. with the upcoming type inferencer or typed variables
intdbl: initialize int+dbl vtables, add I+D sig types

int+dbl vtables derive now from number, not obj.
Still a couple of problems
Fix all tests: a literal int is still just a Number,

not an Integer. It is easier that way still. The type inferencer or
excplicity types will make them Integer then. Ditto for step, times, to.

Add a number? method.