(Binary Analysis) Split InsnSemanticsExpr::equal_to() into two methods

equal_to() renamed to must_equal(); added may_equal().  This makes
InsnSemanticsExpr similar to other instruction semantics classes.
(Binary Analysis) Changed output format for SymbolicSemantics::SValue
(Binary Analysis) Better support for McCarthy vs. non-McCarthy

SymbolicSemantics can represent memory reads as either McCarthy
expressions or new unbound variables when the read address aliases
multiple memory cells.  This behavior can be changed at run-time
via CellCompressor functors.
(Binary Analysis) Yices test case sets SMT solver for new API
(Binary Analysis) Added Yices exe tests using new semantics API

Also added symbolicSemanticsFilter to make it easier to compare
outputs from different kinds of symbolic semantics.
(Binary Analysis) Added new API tests for Yices library