Fixes bug #65633 (built-in server treat some http headers as case-sensitive).

Specifically: php_cli_server_http_reponse_status_code_pair →
php_cli_server_http_response_status_code_pair.

This previously used a buggy implementation of binary search that would loop
infinitely for unknown codes when searching in reason arrays of particular
sizes (such as the one we have at the moment). Since C provides bsearch(),
we'll just use that instead, since libc authors hopefully get this right.

There was also an additional bug that was masked by the first one: the design
was that an unknown code would result in get_status_string() returning NULL,
which would then result in a segfault in append_http_status_line(), since it
assumed that it would always receive a valid string pointer that could be
handed off to smart_str_appends_ex(). We'll now return a placeholder in that
case.

Fixes bug #65066 (Cli server not responsive when responding with 422 http
status code).

Signed-off-by: Anatol Belski <ab@php.net>

Added descriptions for the new HTTP codes:

- 428 Precondition Required
- 429 Too Many Requests
- 431 Request Header Fields Too Large
- 511 Network Authentication Required

fdset management using bit operator is broken on non-x86 arch
and cause built-in server the enter an infinite loop of "select"
and never handle any request.