fts-solr: Fixed HTTPS support by properly propagating SSL client settings from mail_user.

fts-solr: Fixed memory leak at user deinit.

fts-solr: Crashfixes

fts-solr: Use built-in lib-http instead of libcurl. Removed libcurl dependency.

fts: Redesigned/enhanced FTS API and how virtual plugin works with it. The changes include: - Only indexer process and "doveadm index" do FTS indexing now. Other processes connect to the indexer process via UNIX socket and request indexing a specific mailbox. - FTS backends can now index/search any search key. Current backends implement indexing for some specific header fields (Subject, From, To, Cc, Bcc), but it would also be possible to add indexing for e.g. message size or date. - CLucene support is fixed and fully functional. - Solr is split to "solr" and "solr_old" backends. The new "solr" backend supports the new header fields. It also uses mailbox GUIDs as mailbox identifiers, so that renaming a mailbox doesn't require reindexing. The "solr_old" uses the old Solr schema and doesn't support any new features.

fts: Added support for handling multiple namespaces. --HG-- branch : HEAD

Finished making full text search indexes work fast with virtual mailboxes. --HG-- branch : HEAD

Initial support for getting full text search working nicely with virtual mailboxes. --HG-- branch : HEAD

Added support for sorting by X-SCORE. Currently it's only set by fts-solr. --HG-- branch : HEAD

fts-solr: Added break-imap-search setting to use Solr with SEARCH TEXT/BODY parameters. This makes the SEARCH non-compliant with standard IMAP protocol, because TEXT/BODY require support for substring searches and Lucene doesn't support them. --HG-- branch : HEAD

fts-solr: Error handling fixes. --HG-- branch : HEAD

Initial code to support Apache Solr (Lucene indexing server). --HG-- branch : HEAD