fix compile without jpeg

im_jpeg2vips.c failed to compile if jpeglib.h was missing, thanks
Alessandro

ChangeLog

@@ -2,6 +2,7 @@
 - removed some left-over debugging code from configure.ac
 - better handling of args without values, thanks Ruven
 - better error messages from vips.c
+- im_jpeg2vips.c builds without jpeglib.h, thanks Alessandro
 
 6/2/13 started 7.32.1
 - fix --without-lcms, thanks speckins

libvips/deprecated/im_jpeg2vips.c

@@ -44,13 +44,15 @@
 #include <vips/intl.h>
 
 #include <stdlib.h>
+#include <setjmp.h>
 
 #include <vips/vips.h>
 
-#include <setjmp.h>
+#ifdef HAVE_JPEG
 #include <jpeglib.h>
 #include <jerror.h>
 #include "../foreign/jpeg.h"
+#endif /*HAVE_JPEG*/
 
 static int
 jpeg2vips( const char *name, IMAGE *out, gboolean header_only )
@@ -116,7 +118,8 @@ jpeg2vips( const char *name, IMAGE *out, gboolean header_only )
 		header_only, shrink, fail_on_warn ) )
 		return( -1 );
 #else
-	vips_error( "im_jpeg2vips", _( "no JPEG support in your libvips" ) ); 
+	vips_error( "im_jpeg2vips", 
+		"%s", _( "no JPEG support in your libvips" ) ); 
 
 	return( -1 );
 #endif /*HAVE_JPEG*/