Use integers for syntax-pps-stats

Use integers for syntax-pps-stats

* lisp/emacs-lisp/syntax.el (syntax-ppss-stats):
Use integers, not floating-point, for stats, now that integers are
unbounded.  Almost always these should be fixnums.  Add 1 to last
slot’s car so that this addition need not be done at runtime.
(syntax-pps-stats, syntax-ppss): Use integers for calculations.
(syntax-ppss--update-stats): New convenience function.
(syntax-ppss): Use it.