block SIGINT in simulator to aid debugging
pass RIG_SIMULATOR var as path to libtool when spawning simulator
remove unused rig_engine_sync_slaves() function
slave: fix loading and editing the ui

This ensures that the ids we use for loading a ui in a slave device
correspond to edit-mode object pointers within an editor. Instead of
applying edit operations in a slave, separate from where we forward the
same operations to the simulator, we now apply slave operations in sync
with the rate that they are sent to the slave's simulator.
directly use RigControllerMethod enum for serializing ops method
controller-view: don't deref null label, sorting objects
Re-license most of Rig under the MIT license

All of the code in Rig whose copyright is owned by Intel Corporation,
has been re-licensed under the MIT license.

Note: Some code is based on code from Cogl which has multiple copyright
owners but Cogl is itself now also licensed under the MIT license so
this change is compatible.

Note: A few files haven't yet been re-licensed because they currently
contain code based on LGPL code that we don't own the copyright for.
This includes rut-text.c/h and rut-text-buffer.c/h which are based on
code from Cluter; rut-utils.c which contains
rut_util_distribute_natural_allocation() based on code from Gtk, and
rut-box-layout.c where allocate_cb() was originally based on code from
gtkbox.c and although it is now quite different, it might still be
considered to derive from that code.

Details about the copyright licenses can be found in the COPYING file.