Improved the method for matching the `then` and `else` branches when
creating the AST node for the `IfEqualNode`.
Also converted the name of an auxiliary pass to the convention.
Add a pass which removes the `unexpectedpc` as successor of the `switch`
instructions. This simplifies the subsequent analyses.
This pass also removes the unreachable basic blocks dandling around (as
the `unexpectedpc` and `anypc` blocks when they are not needed).
Andrea Gussoni