kcm_formats: Do not write out an unusable value for the "C" locale
Review Request #125984 - Created Nov. 7, 2015 and submitted
See the referenced bug. The special locale value "C" needs to be written out as simply that and not with an encoding suffix added, otherwise the resulting value is not accepted by the locale system.
Built plasma-desktop with these changes, reset 'kcmshell5 formats' settings, checked correct operation of desktop and of CLI and GUI applications.