Fix: The window title wasn't displayed when "Display full path" option was used.

This option was broken after bd905fce40009a950c754486133ab89da2c9919d.

This commit fixes ticket #3394.
Fix: the window title was wrong in capture mode when "Display full path / file name" was used.
Cosmetics: Don't use "m_" prefix for function variables.
Use pipe:stdin instead of pipe:0 to get clearer OSD message and window title.