undefine alloc functions for C extensions

	per guidance in doc/extension.rdoc, these classes now undefine their
	alloc functions:

	- ObjectSpace::InternalObjectWrapper
	- Socket::Ifaddr
	---
	 ext/objspace/objspace.c | 1 +
	 ext/socket/ifaddr.c     | 1 +
	 2 files changed, 2 insertions(+)

The patch is provided by PhobosK (Phobos Kappa).

This should be backported to Ruby 3.0.

[Feature #17187]

* Use the wrapper of rb_cObject instead of data access
* Replaced rest of extentions
* Updated the version guard for Data
* Added the version guard of rb_cData

:resolv_timeout of TCPSocket.new is not implemented for now.

Add connect_timeout to TCPSocket.new in the same way as Socket.tcp.

Closes [Feature #17187]

getaddrinfo_a() gets stuck after fork().
To avoid this, we need 1 second sleep to wait for internal
worker threads of getaddrinfo_a() to be finished, but that is unacceptable.

[Bug #17220] [Feature #17134] [Feature #17187]

Previously, rb_getaddrinfo_a_before_exec() is called from before_exec().
However, the function needs to be called only before fork().
The change moves it to before_fork().

After 94d49ed31c, TestSocket#test_getaddrinfo_after_fork fails in some
platforms. To avoid this, the change extends sleep time to 1.5 second.

We need stop worker threads in getaddrinfo_a() before fork().
This change adds a hook before fork() that cancel all outstanding requests
and wait for all ongoing requests. Then, it waits for all worker
threads to be finished.

Fixes [Bug #17220]