* include/libvirt/libvirt.h.in, src/libvirt.c: add
virNetworkGetBridgeName() to allow finding out what
bridge to connect to in order to join a network.
* src/driver.h: add networkGetBridgeName() to vtable.
* qemud/protocol.h: add the request and reply to
the qemud protocol.
* qemud/dispatch.c, qemud/driver.[ch]: handle them
here.
* src/qemu_internal.c: implement GetBridgeName()
in the qemu driver.
* src/libvirt_sym.version: add new symbol.