Remove magic JPEG variables from ConnParams

Custom compression level and JPEG on/off are not inherent parts of
the protocol negotiation so they do not belong in ConnParams. Let the
UI frontend handle such things instead.
diff --git a/vncviewer/CConn.cxx b/vncviewer/CConn.cxx
index c5cd4a4..789cf09 100644
--- a/vncviewer/CConn.cxx
+++ b/vncviewer/CConn.cxx
@@ -89,11 +89,15 @@
   cp.supportsExtendedDesktopSize = true;
   cp.supportsDesktopRename = true;
 
-  cp.customCompressLevel = customCompressLevel;
-  cp.compressLevel = compressLevel;
+  if (customCompressLevel)
+    cp.compressLevel = compressLevel;
+  else
+    cp.compressLevel = -1;
 
-  cp.noJpeg = noJpeg;
-  cp.qualityLevel = qualityLevel;
+  if (!noJpeg)
+    cp.qualityLevel = qualityLevel;
+  else
+    cp.qualityLevel = -1;
 
   if(sock == NULL) {
     try {
@@ -619,16 +623,19 @@
 
     if (encNum != -1)
       self->currentEncoding = encNum;
-
-    self->cp.qualityLevel = qualityLevel;
   }
 
   self->cp.supportsLocalCursor = true;
 
-  self->cp.customCompressLevel = customCompressLevel;
-  self->cp.compressLevel = compressLevel;
+  if (customCompressLevel)
+    self->cp.compressLevel = compressLevel;
+  else
+    self->cp.compressLevel = -1;
 
-  self->cp.noJpeg = noJpeg;
+  if (!noJpeg && !autoSelect)
+    self->cp.qualityLevel = qualityLevel;
+  else
+    self->cp.qualityLevel = -1;
 
   self->encodingChange = true;