urldata: remove unused struct fields, made more conditional

urldata: remove unused struct fields, made more conditional

- source_quote, source_prequote and source_postquote have not been used since
  5e0d9aea3; September 2006

- make several fields conditional on proxy support

- make three quote struct fields conditional on FTP || SSH

- make 'mime_options' depend on MIME

- make trailer_* fields depend on HTTP

- change 'gssapi_delegation' from long to unsigned char

- make 'localportrange' unsigned short instead of int

- conn->trailer now depends on HTTP

Closes #10147