#110 Compile error bltImageFmt.c, GIF requires setjmp.h

[Bob Techentin]

When compiling bltImageFmt.c from CVS 1.38 on HPUX, I
get an error 'type of jmpbuf undefined' at line 640.
The GifMessage struct requires <setjmp.h>, but this is
not included unless you've got WIN32 or HAVE_LIBJPEG
(lines 82 and 91).

setjmp.h needs to be included for GIF code, whether or
not JPEG format is defined.