Auto-generate XS files by generate.pl script

Add a feature to make XS files from generate.pl tool.
Invoking generate.pl with --generate option builds
XS files from templates in template/ directory into
xs/ directory, using parsed C header files.
Refactor token object from arrayref to hashref.

When lexing function declartions in C header file from
generate.pl script, token objects were constructed by
simple unblessed arrayref. But source code is hard to
understand as its attribute names are replaced by index
numbers. Refactor this to hashref so that attributes
can be named.
Use well-generated datas of C functions instead of just parsed string in template function

When generating XS code with template engine, the process_xs() should
not suffer from converting parsed AST nodes to useful strings, but
fdecl_parse() instead is fixed to return meaningful values.
Remove joke code
Bless AST objects with proper class names attached for comprehension
Remove an unneeded variable