SQLite3::loadExtension() in PHP 7 Appends Extra ".so" to Extension Filename

From manual page: https://www.php.net/manual/en/sqlite3.loadextension.php

When using PHP 7’s SQLite3 extension, the method SQLite3::loadExtension() improperly appends an additional ".so" to the filename provided, leading to load failure. While the SQLite CLI correctly loads the SQLite3 extension without requiring any file extension (e.g., sqlite> .load ./libsqlite_hashes, thus automatically appending the extension when needed), PHP 8 requires specifying the file extension, e.g., SQLite3::loadExtension('libsqlite_hashes.so'). Lastly, PHP 7 fails to load the SQLite3 extension with or without specifying the file extension as it ends up looking for a file with a double extension (e.g., libsqlite_hashes.so.so).

Reproducing steps can be found at https://github.com/nyurik/sqlite-hashes/issues/71

Notice that, loadExtension won't work in any PHP version (7 or 8) if the extension part of the SQLite 3 extension filename is omitted.

This behavior is not properly documented in the manual, which claims support for a broad range of PHP versions (PHP 5 >= 5.3.0, PHP 7, PHP 8) and do not emphasize the importance of specifying the file extension (e.g., .so for Linux).

Start with the SQLite3::loadExtension() manual page and compare its PHP 7 and PHP 8 behavior with the reproduction described in nyurik/sqlite-hashes issue 71. Update the documentation to explain when the shared-library extension, such as .so, must be included and accurately describe the supported PHP versions; done means the version-specific filename requirement is clear.