bug#25979: 25.1; be able to have buffer of same name use same text scaling when re-created

[Drew Adams <drew.adams@oracle.com>]

Use `C-h v' or whatever to show buffer *Help*.

Use `C-x C--' t shrink display of *Help*.

Use `C-h v' or whatever to show buffer *Help* again, for something
different.  The text is no longer scaled the same as it was.

Enhancement request: Add a user option to let someone choose to impose
the same text scaling on the same buffer (or another buffer of the same
name), when it is redrawn (or re-created).

(This just extends the idea that text scaling applies to all displays of
the same buffer, i.e., it is buffer-dependent, not window-dependent or
dependent on something else.)

In GNU Emacs 25.1.1 (x86_64-w64-mingw32)
 of 2016-11-15
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --without-dbus --without-compress-install 'CFLAGS=-O2
 -static -g3''