if comment-end is 2 chars, assume it does end a comment.
Otherwise, scan back to previous comment-end to see if there's
a comment starter between. Also record whether the string quotes
between the start and the end are paired and uniform.
If so, skip to comment starter. If not, scan from start of
defun to find comment starter if any.
(find_defun_start): New function.
Don't modify comstyle inside that loop.
If string quotes don't match up, don't take value from OFROM;
instead, parse forward using scan_sexps_forward.
(scan_sexps_forward): Return value via a pointer passed in.
New element in state contains char addr of last comment-starter seen.
(Fparse_partial_sexp): Change call to scan_sexps_forward.
