perf: Set session.cache_limiter at runtime to avoid clients caching static assets served by PHP

By default there is a Pragma: no-cache header set due to the default
value `no-cache` of session.cache-limiter, which will cause Chrome and
iOS to not cache even with a different Cache-Control header set on the
response.

Signed-off-by: Julius Härtl <jus@bitgrid.net>

lib/private/Session/Internal.php

@@ -52,6 +52,7 @@ class Internal extends Session {
 	public function __construct(string $name) {
 		set_error_handler([$this, 'trapError']);
 		$this->invoke('session_name', [$name]);
+		$this->invoke('session_cache_limiter', ['']);
 		try {
 			$this->startSession();
 		} catch (\Exception $e) {