Disable PEAR by default

Hi internals, I would like to suggest that installation of PEAR is disabled by default in PHP 7.4. PR: https://github.com/php/php-src/pull/3781 I think the reasons for this should be obvious. It's not really the recent security breach itself, but rather the underlying issue that PEAR simply isn't actively maintained anymore. Currently PEAR is broken on master due to the removal of each(), which was deprecated in PHP 7.2. Apparently, since that time nobody noticed that PEAR is throwing deprecation errors, or at least nobody bothered to fix them. (I've submitted https://github.com/pear/Console_Getopt/pull/3 to fix at least this particular issue.) It's somewhat unfortunate that PEAR and PECL are coupled projects, but I don't think that should prevent us from changing this default. Regards, Nikita