Has frequent intermittent failures with:

ERROR: The NOTICE does not match expected message:
- PATTERN: /^\[\d\d-\w\w\w-\d{4} \d\d:\d\d:\d\d\] NOTICE: Terminating ...$/
- MESSAGE: [04-Aug-2020 08:15:37] WARNING: [pool unconfined_status] server reached max_children setting (2), consider raising it
- EXPECT: 'Terminating ...'
- ACTUAL: '2020 08:15:37] WARNING: [pool unconfined_status] server reached max_children setting (2), consider raising it'

This option allows getting status from different endpoint (e.g. port
or UDS file) which is useful for getting status when all children are
busy with serving long running requests.

Internally a new shared pool with ondemand process manager is used. It
means that the status requests have reserved resources and should not
be blocked by other requests.

In practice, we always act as an HTTP/1.1 client, for compatibility
with servers which ignore protocol version. Sending the version in
the request will avoid problems with servers which don't ignore it.

HTTP/1.0 can still be forced using a stream context option.

Closes GH-5899.

* PHP-7.4:
  Prevent test case from stalling

If the CTRL-C event can't be sent to the child for whatever reason, the
test will never terminate, because `proc_close()` waits for an infinite
amount of time.  Therefore, we `proc_terminate()` the child instead,
after explicitly closing the pipes.

* PHP-7.4:
  Fix #77932: File extensions are case-sensitive

* PHP-7.3:
  Fix #77932: File extensions are case-sensitive

The file extension to mime type mapping *must* not depend on the file
extension's case for case-insensitive file systems, and *should* not
for case-sensitive file systems.