Revert the classic grammar and lexer to master.

This makes two small changes to the classic grammar since
BlockExpression should be used instead of ASTArray for 
sequences of expressions to make AST comply with both grammars.
Reverts test of parser and lexer to master version.
Correct formatting of concatentated string in ast tree dumper.

Spaces where missing for some kinds of ast models.
Fix interpolation problem (false detection of function call).

This corrects the lexing of interpolated string. A $x should never be
taken as a function call - i.e. $x(foo) is not a call to function x,
but ${x(foo)} is.
Increase test coverage of the egrammar lexer.

Basically, a copy of the examples for the classic lexer, but
with the egrammar's expanded token set.

TODO: should add more .pp files to lex with newer constructs (will
not increase coverage, but ensures testability of only the lexer).

Adds copy of fixture files instead of reusing them (to enable
future additions of extended lexing capabilities).

Also tests check positioning information.