Several small fixes.

Opening a PR for a bunch of small fixes so that they get reviewed.
Not quite sure why you are doing `${XMETHOD##*/}`... If it's a sanity check, can we do something like this instead?
`if [ "${XMETHOD##*/}" != "$XMETHOD" -o ! -f "$xserverrc" ]`

(or even separate the 2 tests, and print `X11 backend '$XMETHOD' does not exist.` in the second case)