Builtin / default constants

[phorward]

With Tokay v0.5, the language is entering a phase where modularity becomes an important part.

For example, the new builtin native tokens Int and Float can be grouped by a pure Tokay parselet Number, defined as

Number : Float | Int

And together with #10, generic parselets are needed in various ways to provide tools for different use-cases.

Currently, there is no way to define such default parselets, except hacking directly in Compiler::get_constant() or Compiler::set_constant() as with the Whitespace defaults handling.

For sure, Float and Int could either be implemented in pure Tokay code on their own, but this may end in performance lose.

Ideas for this issue (partly from #10):

• Number: Float | Int
• Token: Word | Number | AsciiPunctuation
• Until : @<P, Escape: Void>
• String: @<Start, End: void, Escape: void>
• Repeat : @<P> min=1, max=0
• Not : @<P>
• Peek : @<P>
• Expect : @<P> msg=void
• Separated : @<P, Separator: ',', empty: true>
• Csv : @<Separator: ';'|','|'\t'|' ', String: '"'>

[phorward]

First step towards this is done by 38a130d

[phorward]

Token-parselet added by 8ff20f7.