Move computeScreenLayout/setScreenLayout to unixcommon lib
These two code blocks are not specific to Xvnc/vnc.so, but useful for
x0vncserver as well. RandrGlue.h defines the interface on which
unixcommon depends on.
diff --git a/unix/CMakeLists.txt b/unix/CMakeLists.txt
index 8b2c70e..7a1457d 100644
--- a/unix/CMakeLists.txt
+++ b/unix/CMakeLists.txt
@@ -1,5 +1,5 @@
add_subdirectory(tx)
-
+add_subdirectory(common)
add_subdirectory(vncconfig)
add_subdirectory(vncpasswd)
add_subdirectory(x0vncserver)