Fix typo

I misunderstood the return value from `snprintf()`, which is NOT number
of characters written in buffer, but the number of character the buffer
has to have to write the complete output.

But when `MRB_WITHOUT_FLOAT` is set, there's no way to sleep for
sub seconds. So mruby specific `usleep` is provided.

 * Method implementation functions made `static`.
 * Function declaration style has been changed.
 * Unnecessary header file `mrb_sleep.h` removed.
 * Used `mrb_get_args()` instead of self parsing.
 * Indentation kept untouched.

Support verbose mode in bintest.

`argv` may be retrieved from an array whose `ptr` is `NULL` when it`s
empty.

This reverts commit c96def7c.
This change was from my misunderstanding.

This change was inspired by [ruby-bugs#7573]

Avoid root fiber initialization for CRuby.

closes #4085.

Reversing gems final

It causes trouble for safe navigation operator.

But `BasicObject#__send__` is still available from the core.

The bytecode format was updated so the header version constants must be
updated as well.

Unlike `mrb_check_hash_type()` that returns `nil` if the argument is
not a `Hash`, `mrb_ensure_hash_type()` raises a `TypeError` exception.

We assume meta-programming is less used in embedded environments.
We have moved following methods:

 * Kernel module
   global_variables, local_variables, singleton_class,
   instance_variables, instance_variables_defined?, instance_variable_get,
   instance_variable_set, methods, private_methods, public_methods,
   protected_methods, singleton_methods, define_singleton_methods

 * Module class
   class_variables, class_variables_defined?, class_variable_get,
   class_variable_set, remove_class_variable, included_modules,
   instance_methods, remove_method, method_removed, constants

 * Module class methods
   constants, nesting

Note:
Following meta-programming methods are kept in the core:

 * Module class
   alias_method, undef_method, ancestors, const_defined?, const_get,
   const_set, remove_const, method_defined?, define_method

 * Toplevel object
   define_method

`mruby-metaprog` gem is linked by default (specified in default.gembox).
When it is removed, it will save 40KB (stripped:8KB) on x86-64
environment last time I measured.

This problem only appears when `mrb` executed multiple times (i.e. `mirb`)

Use `uint32_t` instead. Theoretically `uint32_t` can overflow as well,
but I think it is sufficient size for embeddable Ruby VM.

This commit also fix #4096.