For QT applications you need to edit this file:
/usr/share/X11/locale/en_US.UTF-8/Compose
and change every accented Cs by their corresponding Ç and ç (two times), in these lines:
<dead_acute> <C> : "Ç" U0106 # LATIN CAPITAL LETTER C WITH ACUTE <dead_acute> <c> : "ç" U0107 # LATIN SMALL LETTER C WITH ACUTE
For QT applications you need to edit this file:
/usr/share/ X11/locale/ en_US.UTF- 8/Compose
and change every accented Cs by their corresponding Ç and ç (two times), in these lines:
<dead_acute> <C> : "Ç" U0106 # LATIN CAPITAL LETTER C WITH ACUTE
<dead_acute> <c> : "ç" U0107 # LATIN SMALL LETTER C WITH ACUTE