mb_ereg()/mb_eregi() currently have an inconsistent return value
based on whether the $matches parameter is passed or not:

> Returns the byte length of the matched string if a match for
> pattern was found in string, or FALSE if no matches were found
> or an error occurred.
>
> If the optional parameter regs was not passed or the length of
> the matched string is 0, this function returns 1.

Coupling this behavior to the $matches parameter doesn't make sense
-- we know the match length either way, there is no technical
reason to distinguish them. However, returning the match length
is not particularly useful either, especially due to the need to
convert 0-length into 1-length to satisfy "truthy" checks. We
could always return 1, which would kind of match the behavior of
preg_match() -- however, preg_match() actually returns the number
of matches, which is 0 or 1 for preg_match(), while false signals
an error. However, mb_ereg() returns false both for no match and
for an error. This would result in an odd 1|false return value.

The patch canonicalizes mb_ereg() to always return a boolean,
where true indicates a match and false indicates no match or error.
This also matches the behavior of the mb_ereg_match() and
mb_ereg_search() functions.

This fixes the default value integrity violation in PHP 8.

Closes GH-6331.

* PHP-7.4:
  Fix #64076: imap_sort() does not return FALSE on failure

* PHP-7.3:
  Fix #64076: imap_sort() does not return FALSE on failure

If unsupported `$search_criteria` are passed to `imap_sort()`, the
function returns an empty array, but there is also an error on the
libc-client error stack ("Unknown search criterion: UNSUPPORTED
(errflg=2)").  If, on the other hand, unsupported `$criteria` or
unsupported `$flags` are passed, the function returns `false`.  We
solve this inconsistency by returning `false` for unsupported
`$search_criteria` as well.

Closes GH-6332.

These functions only accept 4 params.

These set the PGSQL_DML_EXEC flag by default.

We don't want an explicit null name hit the !name_len check.

These arguments were declared nullable in stubs (and should be
nullable), but didn't accept null in zpp.