The attached patch makes `switch-to-buffer(-other-(window|frame))'
with a prefix arg act analogously to `find-alternate-file': the buffer
current before the switch is killed.

In GNU Emacs 24.3.50.2 (i686-pc-mingw32)
 of 2013-11-28 on LEG570
Bzr revision: 115271 rgm@gnu.org-20131128203155-qjc1xsp19z2k64b2
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --enable-checking 'CFLAGS=-O0 -g3' CPPFLAGS=-DGLYPH_DEBUG=1'