Style fixes for floating-point doc.

Style fixes for floating-point doc.

* commands.texi, customize.texi, display.texi, elisp.texi, files.texi:
* frames.texi, hash.texi, internals.texi, keymaps.texi, lists.texi:
* minibuf.texi, nonascii.texi, numbers.texi, objects.texi, os.texi:
* processes.texi, streams.texi, strings.texi, text.texi:
* variables.texi, windows.texi:
Hyphenate "floating-point" iff it precedes a noun.
Reword to avoid nouns and hyphenation when that's easy.
Prefer "integer" to "integer number" and "is floating point"
to "is a floating point number".
Prefer "@minus{}" to "-" when it's a minus.