util.sql: SQLCipher support

This enables use of encrypted databases if LuaDBI or LuaSQLite3 has been
linked against SQLCipher. Using `LD_PRELOAD` may work as well.

Requires SQLCipher >= 4.0.0 due to the use of UPSERT

CHANGES

@@ -46,6 +46,7 @@ TRUNK
 - New 'keyval+' combined keyval/map store type
 - Performance improvements in internal archive stores
 - Ability to use SQLite3 storage using LuaSQLite3 instead of LuaDBI
+- SQLCipher support
 
 ### Module API
 

util/sql.lua

@@ -84,6 +84,12 @@ function engine:connect()
 	dbh:autocommit(false); -- don't commit automatically
 	self.conn = dbh;
 	self.prepared = {};
+	if params.password then
+		local ok, err = self:execute(("PRAGMA key='%s'"):format(dbh:quote(params.password)));
+		if not ok then
+			return ok, err;
+		end
+	end
 	local ok, err = self:set_encoding();
 	if not ok then
 		return ok, err;

util/sqlite3.lua

@@ -114,6 +114,12 @@ function engine:connect()
 	if not dbh then return nil, err; end
 	self.conn = dbh;
 	self.prepared = {};
+	if params.password then
+		local ok, err = self:execute(("PRAGMA key='%s'"):format((params.password:gsub("'", "''"))));
+		if not ok then
+			return ok, err;
+		end
+	end
 	local ok, err = self:set_encoding();
 	if not ok then
 		return ok, err;