Fix brokennes from clang-format

The template system used for generating CharacterWidth.cpp and
clang-format don't interact that well.

So, repair the things that clang-format broke, disable clang-format for
sections using templates, and don't reenable clang-format until its
notion of indentation is sane.

After this commit the generated file can be easily compared with a
pre-clang-format version:

git diff 7e1b31cd src/characters/CharacterWidth.cpp

The only differences are new clang-format off/on annotations and a few
formatting fixes.