Remove haveSelf include feature

Remove haveSelf include feature

When including a file from another file, its possible to do something
like this:
    include "+some(other)+files"
with the "+" or "|" in the beginning. What will happen then is that
instead of processing the include files separately and then merging into
the existing info, we instead start with the existing info and merge
into it as we go, as if it was written explicitly before the first "+".

It's not particulary clear what this may be useful for. Since it's not
used by xkeyboard-config, not documented anywhere (and google doesn't
bring up anything), completely untested and kind of ugly, remove this
"feature". It most likely never been used.

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