Added search index table + simple XML-based search interface

The XML thing is supposed to be used for auto-completion, of course. The
current search implementation is very, very stupid and simple: Just a
prefix match on the man name, and simple detection of section stuff. I
suppose it'll suffice for now.

util/update_indices.sql

@@ -0,0 +1,9 @@
+-- Create a new table before replacing in order to avoid a long-held lock on
+-- the table being replaced. The site should remain responsive while these
+-- queries are run.
+BEGIN;
+CREATE TABLE man_index_new AS SELECT DISTINCT name, section FROM man;
+CREATE INDEX ON man_index_new USING btree(lower(name) text_pattern_ops);
+DROP TABLE man_index;
+ALTER TABLE man_index_new RENAME TO man_index;
+COMMIT;