Check the file descriptor with `IO#initialize`; resolve #4966

Fix `MRB_TT_CPTR` object with `MRB_NAN_BOXING`

Support `MRB_DISABLE_STDIO` for mruby-pack; ref #4954

 Support `MRB_DISABLE_STDIO` for mruby-sprintf; ref #4954

Fixed a build error in mruby-config

Previously, if `MRB_NAN_BOXING` is defined, for example,
`mrb_cptr_value()` could not keep an odd address.

If it is `MRB_32BIT`, it can be embedded in `NaN` as it is.

If it is `MRB_64BIT`, some operations are shared with `MRB_WORD_BOXING`.
In this case, the MRB_API function `mrb_nan_boxing_cptr_value()` is
defined.

In order to share the same operation with `mrb_float_to_str()`,
the internal structure is modified.

Changed to understand `#`, `0`, `-`, ` ` and `+`.

Based on src/stdio/vfprintf.c in git://git.musl-libc.org/musl

Based on src/stdio/vfprintf.c in git://git.musl-libc.org/musl

The build error occurred when the "build/XXX/bin" directory did not exist.

Merged `cygwin_filename()` into `filename()`.

Validate windows by Dir testing

To prevent infinite loop on errors; reported by @shuujii

build when directories and files have spaces

Modified the build to quote filenames so that it builds when files have spaces

Fix `mrb_funcall_with_block()` uses more GC arena

If `mrb->jmp` is `NULL` and the function `mrb_funcall_with_block()` is
called, GC Arena is returned from the function with over-used.

- A normal (no global exodus) return will consume two GC Arena's.
- In the event of an exception, five GC Arena are consumed.

This patch reduces consumption in both cases to one.

Fix NULL pointer dereferences in mrb_local_variables; fix #4955

However, the behavior of `#call` on the method object of
`local_variables` is not corrected.

Improve configuration guard

ref #4576 and ref #4947

* Need MRBAPI functions without `MRB_DISABLE_STDIO`:
  * mrbgems/mruby-bin-debugger
  * mrbgems/mruby-bin-mirb
  * mrbgems/mruby-bin-mrbc
  * mrbgems/mruby-bin-mruby
  * mrbgems/mruby-bin-strip
* Need `stdio.h`:
  * mrbgems/mruby-io
  * mrbgems/mruby-print
* Need `snprintf()` in `stdio.h`:
  * mrbgems/mruby-pack
  * mrbgems/mruby-sprintf

'stdio.h' is included in 'mruby.h' ('mrbconf.h').

However, keep 'stdio.h' used by mruby-test.

Some rule to CrossBuild Android

Fix the argument of `mrb_file_is_absolute_path()`.

Traditional, UNC, and Drive Path