Release of BlueZ 5.46

This release contains several improvements to GATT support. In particular, there are new D-Bus methods which let an application get a dedicated file descriptor to read/write data from/to a GATT characteristic. There are also fixes in some other areas, such as OBEX and SDP. The release fixes also compiler warnings/errors that show up with GCC 7 (found e.g. in Fedora 26).