For example when the cursor is _on_ the `'` in `'word'`, the cursor
wouldn't move because the search for a matching pair started _from_ the
position of the cursor and simply found itself.
Surround operations previously ignored other pairs that are
enclosed within which should be skipped. For example if the
cursor is on the `,` in `{{a},{b}}`, doing `md{` previously
would delete the `{` on the left of `a` and `}` on the right
of `b` instead of the outermost braces. This commit corrects
this behavior.
