Extract create_module_alias

This pulls out a small piece of parse_constant_body.
Extract stop_at_EXPR_END

I'm unsure what this condition tests, exactly, but it is identically
reused in parse_constant_body
Extract method_parameters_end_token

This also moves a giant comment out of parse_method_or_yield_parameters
Extract get_tkread_clean

This replaces several places where the read tokens were cleaned of
offending text.
Extract parse_method_params_and_body

This was a large chunk of parse_method
Extract parse_symbol_arg_paren

This parses only symbols inside ().
Extract parse_symbol_arg_space

This parses symbol arguments surrounded by spaces.
Fix description of parse_symbol_arg_paren
Remove unneeded args local variable

After refactoring parse_symbol_arg out there's no need to use a local
variable.
Extract get_visibility_information

This gets the visibility type, rdoc visibility symbol and singleton
information.
Extract update_visibility

This sets the visibility for items following the visibility declaration
in the container.
Comment and nodoc parse_meta_method_name

Also, swap the argument order as tk is less important.
Extract parse_meta_method_params

This handles the parameters and block following the metaprogrammed
method declaration.
Use get_end_token in skip_optional_do_...

skip_optional_do_after_expression looks for an end_token the same as
method_parameters_end_token so method_parameters_end_token was renamed
to get_end_token and used in skip_optional_do_after_expression.

This also adds TkRPAREN handling when skipping the do which may cause
future issues (as the nil is not handled).
Mark suspicious code in get_method_container

This is using the local object space to find a constant which may not
exist.  I'm unsure how this is supposed to work since the name likely
won't exist.

It should probably start its lookup from the store.