URI regexp: support ? in query and fragment

The query and fragment components can include question marks in them. As
an example, LDAP URIs have queries of the form:

["?" [attributes] ["?" [scope] ["?" [filter] ["?" extensions]]]]]]

so the following:

ldap://[2001:db8::7]/c=GB?objectClass?one

does a one-level deep query to the LDAP server at IPv6 address
2001:db8::7 for the children of object c=GB and returns their
objectClass attribute.