#15 Source visualization with 'c' and 'Shift+c' does not work unless the source file is already loaded

[Mihai T. Lazarescu]

'c' and 'Shift+c' do not work if the target source file is
not already loaded in an editor tab.

As a workaround one can press 'e' then 'c' works fine for
that file.

Either document the limitation and the workaround or
automatically load the target source file as done for the
'e' command. However, in the later case avoid changing the
current buffer and its edit state.