Fix image corruption issues with, and add a few optimizations for, 16bpp clients


git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@4642 3789f03b-4d11-0410-bbf8-ca57d06f2519
diff --git a/common/rfb/JpegCompressor.cxx b/common/rfb/JpegCompressor.cxx
index 33f6c41..0ed5cb5 100644
--- a/common/rfb/JpegCompressor.cxx
+++ b/common/rfb/JpegCompressor.cxx
@@ -169,7 +169,7 @@
   }
 #endif
 
-  if (pitch == 0) pitch = w * pixelsize;
+  if (pitch == 0) pitch = w * pf.bpp / 8;
 
   if (cinfo.in_color_space == JCS_RGB) {
     srcBuf = new rdr::U8[w * h * pixelsize];