(maint) Fix problem after adding flag to respond_tp? call

The extra flag was not handled by the parser factory. (The flag
is required for Ruby 2.0 since behavior has changed).
(maint) Move Lexer2 to the correct namespace (Puppet::Pops::Parser)

It was named Lexer2 in the gloval namespace.
(perf) Make future parser use new faster lexer

This makes the future parser use the new faster lexer.
As a consequence features provided by the old lexer has now moved
to the parser (keeping track of namestack).

Locator information is still not optimized wrt the parser as the
tokens/locator information are adapter to the "old" way
(room for performance improvements).

Tests are updated as the new lexer is both more restrictive, and in
some case more relaxed (where regular expressions may occur).