Retrascope

Add support of "multiple assignments" that are of the following form:

{x,y,z} = w;

Such assignments should be splitted into simple concurrent (non-blocking) assignments with taking defined variables' order into account.
The result of "multiple expression" (of the above form) processing should be like:

x = bvextract (w, offset_x);
y = bvextract (w, offset_y);
z = bvextract (w, offset_z);