[Tolk] bool type (-1/0 int under the hood)

Comparison operators `== / >= /...` return `bool`.
Logical operators `&& ||` return bool.
Constants `true` and `false` have the `bool` type.
Lots of stdlib functions return `bool`, not `int`.

Operator `!x` supports both `int` and `bool`.
Condition of `if` accepts both `int` and `bool`.
Arithmetic operators are restricted to integers.
Logical `&&` and `||` accept both `bool` and `int`.

No arithmetic operations with bools allowed (only bitwise and logical).

tolk/CMakeLists.txt

@@ -18,6 +18,7 @@ set(TOLK_SOURCE
         pipe-check-rvalue-lvalue.cpp
         pipe-check-pure-impure.cpp
         pipe-constant-folding.cpp
+        pipe-optimize-boolean-expr.cpp
         pipe-ast-to-legacy.cpp
         pipe-find-unused-symbols.cpp
         pipe-generate-fif-output.cpp