Fix compilation in the absence of libjpeg

The JPEG library is not necessarily installed everywhere, and sometimes
it is outright undesirable to compile with JPEG support, e.g. when the
server is not very fast.  So fix the compilation for that case.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

rfb/rfbclient.h

@@ -177,7 +177,6 @@ typedef struct _rfbClient {
 
 
 #ifdef LIBVNCSERVER_HAVE_LIBZ
-#ifdef LIBVNCSERVER_HAVE_LIBJPEG
 	/*
 	 * Variables for the ``tight'' encoding implementation.
 	 */
@@ -196,6 +195,7 @@ typedef struct _rfbClient {
 	char tightPalette[256*4];
 	uint8_t tightPrevRow[2048*3*sizeof(uint16_t)];
 
+#ifdef LIBVNCSERVER_HAVE_LIBJPEG
 	/* JPEG decoder state. */
 	rfbBool jpegError;