Here is an update:
SVN trunk now implemented this feature.
I did not apply your patch since it changed the order of status bar columns - and you missed several locations where messages were sent to a specific column, but thats behind us now
I chose to implement it using a 'lock' icon for read-only files on top of the tab
It would be great to see the status of a file if Codelite could modify the icon for the file in the workspace view. Read only vs writable, checked out of source control or not, modified or not. Also "filters" on the files in the workspace view would be great. Currently I create virtual folders to contain Source Files, Include Files, Make Files, Linker Files, Assembly Files and Map Files.