Add support for constant expressions as operands
This commit also shuffles some code around, but without any other functionality change
specialize icmp comparison per %reg
Multiple fixes to the type inference
 - enforce certain types for icmp and select
 - Minimize type models to avoid infinite loops when Z3 does not deliver minimal models
switch to Z3 SimpleSolver for solving type constraints
Constrain argument to isSignBit to have integer type
disallow definition of new constants/input vars in Target program
add TODO list
Merge pull request #4 from regehr/todo

add TODO list
Merge branch 'master' of https://github.com/nunoplopes/alive
fix typo
minor TODO list updates
minor simplifications to SMT encoding
consolidate another test
enhance parsing of comments
Add framework for error diagnostics
fix line numbers in error messages
Improve display of errors generated by the parser
Another round of improvements to error handling
fix a crash with width(%foo) in expressions
fix build