Improve documentation for integer and floating-point basics.

Improve documentation for integer and floating-point basics.

* numbers.texi (Numbers, Integer Basics, Float Basics):
Document the basics a bit more precisely.  Say more clearly
that Emacs floating-point numbers are IEEE doubles on all
current platforms.  Give more details about frexp.
Say more clearly that '1.' is an integer.
(Predicates on Numbers): Fix wholenump typo.
* objects.texi (Integer Type): Adjust to match numbers.texi.