Fix for bug #12547.
- "Interword" becomes "Normal"
- "Protected" becomes "Non-Breaking"
Plus a minor fixes to the "Horizontal Space Settings" dialog:
- Indicate that when "Non-Breaking" is disabled, the space will be non-breaking
In particular, the directory frontends/qt4 is renamed to frontends/qt.
Many configurations file have to be updated. All mentions of qt4 in
the source have been audited, and changed to qt if necessary.
The only part that has not been updated is the CMake build system.