The old size of `struct RBreak` was 56 bytes (`MRB_NO_BOXING`)
and it's bigger than other object structures. That increase the
size of `RVALUE` thus increase the total amount of memory consumption.

Now the method tables (in classes/modules and caches) keeps C function
pointers without wrapping in `struct RProc` objects. For the sake of
portability, `mrb_method_t` is represented by the struct and union, but
if the most significant bit of the pointer is not used by the platform,
`mrb_method_t` should be packed in `uintptr_t` to reduce memory usage.

`MRB_METHOD_TABLE_INLINE` is turned on by default for linux.

It's fixed since 1.3.0

Since no ISO classes/methods are not provided by mruby, there's
no use mentioning `Kernel.binding` here.

Removed useless condition

implement Array.transpose

Cosmetic changes in variable.c

Not from the execution ensure proc; fix #3849

You should not access `mrb->c->ci->argc` directly.

The outer class of the class/module definition should be taken from
`MRB_TARGET_CLASS(mrb->c->ci->proc)` not `mrb->c->ci->target_class`
which is the target of constant lookups.

Otherwise half-baked string object will be allocated.

Merge branch 'mrb_without_float' of https://github.com/pandax381/mruby into pandax381-mrb_without_float

Make `block_given?` to search for the top of the scope first.
The top of the scope means either:

* the top method body
* the enclosing class body
* the top-level

The special case is the method defined by `define_method` with a
block as in #3841. In cases like this, the method body (given by
a block) is not considered as the top of the scope. You need to use
`&block` in the block parameter if you want to know if a block is
given to the method.

This commit also changes the behavior of `MRB_PROC_SCOPE` flag.
Now it is only set if the `proc` is either a class body or a method
body defined in Ruby. It is no longer set for a block that given to
`define_method`.

When `block_given?` is called from a block given to `define_method`
as a method body, the `bidx` may not be within `env` saved closure.
In this case, it causes heap buffer overflow.

Also removed the code to normalize NaN value for `MRB_NAN_BOXING`.
Tha code was added to fix #1712 but no longer required after 249f05e7.

This strings in `irep` pools may be freed forcefully in `mrb_irep_free`.
This commit probably fixes #3817 as well.

don't strip away backtrace info when an exception is re-thrown

Unlike method definition, constant reference should start from
`MRB_PROC_TARGET_CLASS(ci->proc)`, not `ci->target_class`.
In addition, `MRB_PROC_TARGET_CLASS(ci->proc)` is always set.

The destination `proc` may be an orphan.