Remove full support for colour maps

Gets rid of a loooot of code and complexity.

Colour map clients are still supported through an
automatically generated map, but we lose the ability to
develop a client or server that uses colour maps
internally.
diff --git a/tests/pixelconv.cxx b/tests/pixelconv.cxx
index ef9d3aa..1d19b88 100644
--- a/tests/pixelconv.cxx
+++ b/tests/pixelconv.cxx
@@ -101,7 +101,7 @@
   if (srcpf.isLittleEndian()) {
     delete pt;
     pt = new rfb::PixelTransformer;
-    pt->init(srcpf, NULL, dstpf);
+    pt->init(srcpf, dstpf);
   }
 
   printf("%s,%s", srcb, dstb);