net/pear-Net_IPv6: Fix for PHP < 8

Previously added patches use str_ends_with(), which is only available
in php 8 and newer. This commit adds to the patch a definition of
str_ends_with() in the case it is undefined in an earlier version.

Sponsored by: Rubicon Communications, LLC ("Netgate")
Differential Revision: https://reviews.freebsd.org/D36219