symbols: fix possible use of uninitialized value

Nothing bad can come out of it, but for some reason this error didn't
return early (inherited from xkbcomp).
Also promote the log message to an error, as it clearly is.

Signed-off-by: Ran Benita <ran234@gmail.com>
symbols: cleanup SetSymbolsField

Normalize the style and error message levels.

Signed-off-by: Ran Benita <ran234@gmail.com>
symbols, keycodes: fix int return type when bool is intended

Signed-off-by: Ran Benita <ran234@gmail.com>