[S15] Add section for identifier and numeric literals.
[S15] Add section for identifier and numeric literals.

The identifier literals is effectively a reiteration of what's already
in S02. The numeric literals a newer concept to Perl 6, and hopefully
the details will be ironed out in short order :) .

tokuhirom/specs,perl6/specs,prammer/specs,tokuhirom/specs,prammer/specs,prammer/specs,tokuhirom/specs,perl6/specs