xkbcomp: escape the section names before storing them in the keymap

This ensures the names are escaped before having any interaction with
the user.

This was caught by noticing dump(compile(dump())) != dump. Since that's
a nice test we add it to stringcomp.

https://bugs.freedesktop.org/show_bug.cgi?id=67032

Reported-By: Auke Booij
Signed-off-by: Ran Benita <ran234@gmail.com>