Added check for php calendar extension.

(Its extension is included in the base php package for Linux.
But, It is not included in FreeBSD by default. So, it should be checked.)

(cherry picked from commit 40171d2db3)

pandora_console/install.php

@@ -565,6 +565,7 @@ function install_step2() {
 			$res += check_extension("json","PHP json extension");
 			$res += check_extension("curl","CURL (Client URL Library)");
 			$res += check_extension("filter","PHP filter extension");
+			$res += check_extension("calendar","PHP calendar extension");
 			if (PHP_OS == "FreeBSD") {
 				$res += check_exists ("/usr/local/bin/twopi","Graphviz Binary");
 			}