fix: include\mruby/gc.h(43): warning C4200: nonstandard extension used: zero-sized array in struct/union

Change DISABLE_STDIO to MRB_DISABLE_STDIO in mruby-time/time.c

After f68f5f6b, the operand of `OP_EPOP` should have been `1`.
Now we have removed the limitation.

fix #3809

If `#initialize` is implemented in C, we don't need stack consuming
`mrb_funcall`.

Instead of `irep -> proc` chain, we use `irep -> irep` chain to
avoid GC bugs like #3804. We added `target_class` reference to
`mrb_irep` struct. That means one more word consumption per `irep`.

Trying to make the code more readable

Update print.c

Strings not containing a newline are not printed synchronously
ex. bin/mruby -e '["a", "b", "c", "\n", "d", "e", "f", "\n"].each {|e| print e ; usleep 200000}'

Trying to make the source code more understandable by removing mixing of ternary if statements with attributions.

Tested local jump errors caused by break in a proc

It may be better to raise exceptions, but CRuby doesn't.

Unless `MRB_NAN_BOXING` is specified.

Allowed to pass multiple exceptions to assert_raise

Refactored #assert_raise and #assert_nothing_raised

This reverts commit 15d48efa.

`__ENCODING__' returns the current encoding name (string), unlike
CRuby that returns the encoding object.

Array refactorings and speed improvements