new file:   church.hpp
	new file:   name-traits.hpp
Added accessors and insert operators
modified:   church.hpp
Renamed and cosmetics.
	new file:   expr-builder.hpp
	deleted:    builtin/builtin.hpp
modified:   ../lambda-interpreter/environment.hpp

Redesigned closure. Now it keeps a pointer to the frame, instead of the
frame structure itself.
	modified:   lambda-interpreter/environment.hpp
	modified:   lambda-interpreter/examples/environment-example.cpp
Major changes in some structures.

struct basic_frame:
	Added typedef

struct indexed_frame:
	Added accessor

struct std_environment:
	Replaced element_type with closure_type
	Added element_iterator type
	Changed closure_type: Now the environment part is a frame, not its reference.
	Disabled some code.
	root member variable is now m_root. Added an accessor.
	Changed the enter() code.
	Changed the constructor code.
	Changed the resolve() code.
Written most of the k-machine emulation semantics templates.
Miscelaneous changes.
Declared name_traits template.
	deleted:    builtin/builtin.hpp