bug#1281: 23.0.60; Info-mode-map should not bind both `backtab' and `S-tab'

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

This first of these bindings should be removed from info.el:
(define-key map [(shift tab)] 'Info-prev-reference)
(define-key map [backtab] 'Info-prev-reference)
 
The second binding should be all that is needed to cover
`S-tab' also (and `S-isolefttab' too).
 
And binding both explicitly requires users, to override the bindings,
to also bind both of these.
 
IOW, to bind `S-TAB' to `foo' effectively, a user must do both of these:
 
(define-key Info-mode-map [(shift tab)] 'foo)
(define-key Info-mode-map [backtab] 'foo)
 
Otherwise, it is likely that the user binding will not take effect. In
this Windows build, for instance, binding only `backtab' means that
`S-TAB' still invokes `Info-prev-reference'.
 
Please also backport this fix to Emacs 22.
 

In GNU Emacs 23.0.60.1 (i386-mingw-nt5.1.2600)
 of 2008-10-09 on LENNART-69DE564
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --no-opt --cflags -Ic:/g/include
-fno-crossjumping'