Leon now matches Scala semantics of Int as 32 bits bit-vectors.
This commits modifies the semantics of IntLiteral to be treated
as 32 bits integer everywhere (solver, evaluator, ...).

Introduces a new literal type, InfiniteIntegerLiteral, representing
a natural integer. The front-end maps the use of BigInt to these
new trees, and the solver properly handles them as mathematical
integers.

The behaviour of many regression tests changes due to this new
semantics. In particular many of them now timeout because they
are no longer proving properties over mathematical integers. This
commit updates the tests to reflect this new semantics.

- evaluate it to simplest value
- solve it to arbitrary value
- Use within CEGLESS as bank of exprs
- Avoid GuidedCloser if non-det expr (contains choose, holes, ..)

Introduces a guiding witness, indicating what the original solution was.
This original solution is then either

1) tried as potential solution (verification)
2) used as decomposition, for instance on If expressions.

Introduces terminates(f(..)) witnesses in the spec, used to generate
safe recursive calls.

After a split i.e. on a List with Cons, the witness becomes

terminates(f(.., Cons(h, t), ..))

at which point we know that calling f(.., t, ..) is safe
termination-wise.

- Introduce Leon strings (smt-based solvers only)
  Available in leon.lang.string._

- Print method calls properly, specialize binary ops

List:
  slice(from: Int, to: Int): List[T]
  replace(from: T, to: T): List[T]
  chunks(s: Int): List[List[T]]
  zip[B](that: List[B]): List[(T, B)]
  -(e: T): List[T]
  --(that: List[T]): List[T]
  &(that: List[T]): List[T]
  pad(s: Int, e: T): List[T]
  find(e: T): Option[Int]
  lastOption: Option[T]
  firstOption: Option[T]
  unique: List[T]
  splitAt(e: T): List[List[T]]
  split(seps: List[T]): List[List[T]]
  count(e: T): Int
  evenSplit: (List[T], List[T])
  insertAt(pos: Int, l: List[T]): List[T]
  replaceAt(pos: Int, l: List[T]): List[T]
  rotate(s: Int): List[T]

ListOps:
  flatten[T](ls: List[List[T]]): List[T]

- NormalizationRule becomes priorities, so that we can have multiple
  distinct layers

- Use the @library annotation, move synthesis stuff to synthesis,
  Oracles.

- Make sure tests use PreprocessingPhase and import synthesis when
  adequate

- Extract proper package objects fix patternRecons and simplifiers

- Reorganize library:
  - leon.{choose,???} -> leon.lang.synthesis
  - leon.{waypoint,epsilon} -> leon.lang.xlang

- Holes become chooses

- Unhandled types are removed, Untyped is now checked for and
  a warning is issued if an untyped expression is found.

- Implement the Leon Library in Leon-land rather than Scala-land.
  import leon.Utils._ becomes import leon.lang._
  import leon.Annotations._ becomes import leon.annontation._

  For now, the library defines generic Options and Lists.
  The library is automatically imported from the ./leon script, unless
  the --library=no option is passed.

- Support parsing of multiple files and modules.

- Introduce new annontations:
    @ignore: remove definition from Leon
    @verified: do not consider for verification unless explicitly
        specified

Methods:
--------

Methods are now supported in ADT roots only (e.g. single case classes or
abstract classes). The phase `MethodLifting` converts them to normal
global functions which makes them transparent to the rest of Leon.

Introducing Leon Library:
-------------------------

Common structures and functionalities can be shipped as part of the
Library.scala file, which is a set of ADTs with methods.

Imported via `import leon.Library._`

New Annotations:
----------------

- @verified means library function will not be considered for verification
  unless specifically given through --functions

- @proxy allows non-pure bodies, which will be silently ignored.
  pre/post need to be in purescala.

Functions without bodies (e.g. proxy methods) are now materialized with
a choose construct automatically, replicating the post-condition. This
allows compilation to bytecode and execution of VCs refering to proxy
methods.

Tree Modifications:
-------------------
- FunDef now have params, not args.

- VarDecl is renamed ValDef.

- Added methods in ClassDef, as well as This and MethodInvocation,
  both are converted to normal function calls by the MethodLifting
  phase.

- Refactor code extraction
  - Standardize extractors
  - Fix type identification by resolving type aliases

- Redo reporter integration with Scalac
  - Fix relining to prevent bizarre compile-errors

- Refactor Pretty-Printers
  - Extensible class interface
  - Not returning mutable string-buffers anymore

- Fixes according to 2.10
    - 100% false warnings in Tests
    - imports for postfix-ops or implicits

- Upgrade ScalaZ3 to 2.10

- Upgrade Cafebabe to 2.10