Set the stage for making the builtin modules more dynamic.
Note: this only converts crypto and net, I will add more extensions in a
later commit.
* node.h: Add utility macro for converting macro values to strings.
* node.h: Include the actual module name inside the module structure, not
just the file it was built from.
* node.h: New Macro, NODE_MODULE_DECL, for declaring an external reference
to a module structure.
* node_extensions.cc: New File, implements get_builtin_module, which
iterates over the module structures that are compiled into node.
* node.cc(node::Binding): Use the new module lookup function to find
modules.
* node_{net,crypto}.c: Add NODE_MODULEs to generate the module structure.
Paul Querna