Add Newspeak type annotation support and local variable initializer expressions

[smarr]

This PR improves overall compatibility with Newspeak in multiple ways, but the main improvements add support for type annotations and local variable initializer expressions.

• parse Newspeak language version marker and module category at beginning of the file
• parse local variable definition with initializer expressions and support definition of immutable local variables
• add support for comments in more places, for instance around keyword messages, slot definitions, unary selectors
• add a warning when value of integer literals with radix does not fit into long, big integers are not supported yet
• allow minus - to be part of operator sequence

Below, some examples for the most noticeable newly supported syntax.

Local Variables with Initializers

Inside of methods, we can now use the slot initializer syntax as in Newspeak:

public bar = (
  | anImmutableInt = 42.
    aMutableInt ::= 43. |
  anImmutableInt:: 4. (* will raise compiler error *)
  aMutableInt:: aMutableInt + 1. (* works as expected *)
)

Type Annotations

Type annotations are supported for slot definitions as well as return types for messages.
These type annotations are currently not checked in anyway, and there are no plans to introduce checks.

For slots, examples are:

public class Foo (|
  public someNumber <Integer> ::= 42.
  public listOfStrings <List[String]> = createList.
  public blockWithValueArg <[:Value]> = [:v | v ].
|)()

For methods, return types can be specified for instance like this:

public class Foo ()(
  public bar ^ <Foo> = (
    ^ self
  )

  public - other ^ <Integer> = (
    ^ 6
  )
  
  public key: a word: b ^ <List[Promise[V, E]]> = (
    ^ List new
  )
)

[coveralls]

Coverage remained the same at 80.051% when pulling ca5afbc on ns-compat into d933bf1 on dev.

[coveralls]

Coverage increased (+0.05%) to 80.101% when pulling eadd962 on ns-compat into d933bf1 on dev.

[coveralls]

Coverage increased (+0.05%) to 80.101% when pulling cd369ee on ns-compat into d933bf1 on dev.