bug#12314: 24.2.50; `add-to-history': use `setq' with `delete'

[Drew Adams]

This line in `add-to-history':
 
(if history-delete-duplicates (delete newelt history))
 
should be this:
 
(if history-delete-duplicates (setq history (delete newelt history)))
 
(Or for more clarity, use `when' instead of `if'.)
 
I'm not 100% sure this is a problem, but it seems to be in a case I saw.
And there seems to be no reason not to set `history' to the `delete'
result here.

In GNU Emacs 24.2.50.1 (i386-mingw-nt5.1.2600)
 of 2012-08-26 on MARVIN
Bzr revision: 109788 dmantipov@yandex.ru-20120827041533-3cy7pdjdqz14o90c
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.6) --no-opt --enable-checking --cflags
 -ID:/devel/emacs/libs/libXpm-3.5.8/include
 -ID:/devel/emacs/libs/libXpm-3.5.8/src
 -ID:/devel/emacs/libs/libpng-dev_1.4.3-1/include
 -ID:/devel/emacs/libs/zlib-dev_1.2.5-2/include
 -ID:/devel/emacs/libs/giflib-4.1.4-1/include
 -ID:/devel/emacs/libs/jpeg-6b-4/include
 -ID:/devel/emacs/libs/tiff-3.8.2-1/include
 -ID:/devel/emacs/libs/gnutls-3.0.9/include
 -ID:/devel/emacs/libs/libiconv-1.13.1-1-dev/include
 -ID:/devel/emacs/libs/libxml2-2.7.8/include/libxml2'