Fix MS-Windows build broken by 2012-09-15T07:06:56Z!eggert@cs.ucla.edu, completing...

Fix MS-Windows build broken by 2012-09-15T07:06:56Z!eggert@cs.ucla.edu, completing fix for bug #12446.

 src/w32xfns.c:
 src/w32uniscribe.c:
 src/w32term.c:
 src/w32select.c:
 src/w32reg.c:
 src/w32proc.c:
 src/w32menu.c:
 src/w32inevt.c:
 src/w32heap.c:
 src/w32font.c:
 src/w32fns.c:
 src/w32console.c:
 src/w32.c:
 src/w16select.c: Remove inclusion of setjmp.h, as it is now included
 by lisp.h.  This completes removal of setjmp.h inclusion
 erroneously announced in the previous commit.
 src/lisp.h [!HAVE__SETJMP, !HAVE_SIGSETJMP]: Make the commentary
 more accurate.
 src/image.c (_setjmp) [!HAVE__SETJMP]: Define only if 'setjmp' is
 not defined as a macro.  The latter happens on MS-Windows.