Support [,;] as separators for multiple search domains with all protocols

This should fix #433 (closed) specifically, as well as prevent any future similar issues for other protocols.

Supported protocols and servers are extremely inconsistent in how they send us multiple search domains. Some provide domains via repeating fields which we glom into a single space-separated string, some provide domains in single fields which contain ',' or ';' as separators.

Since neither ',' nor ';' is a legal character in a domain name, and since all known routing configuration scripts support space-separated domains. we can safely replace these characters with spaces, and thus support all known combinations.

Further analysis of the status quo at #433 (comment 950199540).