Encapsulate screen layout storage in ConnParams

Avoid direct access to the screen dimensions and layout so that we
can make sure it stays sane. This also makes sure the layout is
properly updated when we only get the screen dimensions from the
server.
diff --git a/tests/decperf.cxx b/tests/decperf.cxx
index 9061cb5..24f6604 100644
--- a/tests/decperf.cxx
+++ b/tests/decperf.cxx
@@ -85,7 +85,7 @@
 {
   CConnection::setDesktopSize(w, h);
 
-  setFramebuffer(new rfb::ManagedPixelBuffer(filePF, cp.width, cp.height));
+  setFramebuffer(new rfb::ManagedPixelBuffer(filePF, cp.width(), cp.height()));
 }
 
 void CConn::setPixelFormat(const rfb::PixelFormat& pf)
diff --git a/tests/encperf.cxx b/tests/encperf.cxx
index 4e7038f..a232fb9 100644
--- a/tests/encperf.cxx
+++ b/tests/encperf.cxx
@@ -203,7 +203,7 @@
   CConnection::setDesktopSize(w, h);
 
   pb = new rfb::ManagedPixelBuffer((bool)translate ? fbPF : cp.pf(),
-                                   cp.width, cp.height);
+                                   cp.width(), cp.height());
   setFramebuffer(pb);
 }