runtime(doc): Sort options.txt alphabetically

Related to: vim/vim#13630

1. Sort section 3 (option-summary) of runtime/doc/options.txt in
   alphabetical order.
2. Remove double newlines in section 3 (option-summary).

I did not alphabetically sort ttimeout and ttimeoutlen because they seem
to belong with timeout and timeoutlen respectively, but I would like
some input on that decision.

Signed-off-by: laburnumT <[email protected]>
Signed-off-by: Christian Brabandt <[email protected]>

Author: laburnumT