lib/query: refactor & rework

- Move the lib/query/ stuff up a level into lib/
- Associate directly with the Query object
- Rework the Query object to be C++ rather than mixed with C
- Update all dependencies, tests

lib/mu-xapian.hh

@@ -0,0 +1,40 @@
+/*
+** Copyright (C) 2020 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
+**
+**  This library is free software; you can redistribute it and/or
+**  modify it under the terms of the GNU Lesser General Public License
+**  as published by the Free Software Foundation; either version 2.1
+**  of the License, or (at your option) any later version.
+**
+**  This library is distributed in the hope that it will be useful,
+**  but WITHOUT ANY WARRANTY; without even the implied warranty of
+**  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+**  Lesser General Public License for more details.
+**
+**  You should have received a copy of the GNU Lesser General Public
+**  License along with this library; if not, write to the Free
+**  Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+**  02110-1301, USA.
+*/
+
+
+#ifndef __XAPIAN_HH__
+#define __XAPIAN_HH__
+
+#include <xapian.h>
+#include <mu-parser.hh>
+
+namespace Mu {
+
+/**
+ * Transform a parse-tree into a Xapian query object
+ *
+ * @param tree a parse tree
+ *
+ * @return a Xapian query object
+ */
+Xapian::Query xapian_query (const Mu::Tree& tree);
+
+} // namespace Mu
+
+#endif /* __XAPIAN_H__ */