Import global functions and constants for enhanced performance

This is better for performance because these then don't need to be reevaluated every time they are called.

When encountering an unqualified function or constant reference, PHP will first try to locate a symbol in the current namespace by that name, and then fall back to the global namespace.
This short-circuits the check, which has substantial performance effects in some cases - in particular, ord(), chr() and strlen() show ~1500x faster calls when they are fully qualified.

However, this doesn't mean that PM is getting a massive amount faster. In real world terms, this translates to about 10-15% performance improvement.
But before anyone gets excited, you should know that the CodeOptimizer in the PreProcessor repo has been applying fully-qualified symbol optimizations to Jenkins builds for years, which is one of the reasons why Jenkins builds have better performance than home-built or source installations.
We're choosing to do this for the sake of future SafePHP integration and also to be able to get rid of the buggy CodeOptimizer, so that phar and source are more consistent.

src/pocketmine/utils/Internet.php

@@ -23,6 +23,35 @@ declare(strict_types=1);
 
 namespace pocketmine\utils;
 
+use function array_merge;
+use function curl_close;
+use function curl_error;
+use function curl_exec;
+use function curl_getinfo;
+use function curl_init;
+use function curl_setopt_array;
+use function explode;
+use function preg_match;
+use function strip_tags;
+use function strtolower;
+use function substr;
+use function trim;
+use const CURLINFO_HEADER_SIZE;
+use const CURLINFO_HTTP_CODE;
+use const CURLOPT_AUTOREFERER;
+use const CURLOPT_CONNECTTIMEOUT_MS;
+use const CURLOPT_FOLLOWLOCATION;
+use const CURLOPT_FORBID_REUSE;
+use const CURLOPT_FRESH_CONNECT;
+use const CURLOPT_HEADER;
+use const CURLOPT_HTTPHEADER;
+use const CURLOPT_POST;
+use const CURLOPT_POSTFIELDS;
+use const CURLOPT_RETURNTRANSFER;
+use const CURLOPT_SSL_VERIFYHOST;
+use const CURLOPT_SSL_VERIFYPEER;
+use const CURLOPT_TIMEOUT_MS;
+
 class Internet{
 	public static $ip = false;
 	public static $online = true;