Renamed .inc files to .php files

.inc extension for included PHP files is not recommended, instead
standard .php should be PHP files extension.

diff --git a/lib/xmlrpc.inc b/lib/xmlrpc.php
similarity index 100%
rename from lib/xmlrpc.inc
rename to lib/xmlrpc.php

diff --git a/lib/xmlrpc_wrappers.inc b/lib/xmlrpc_wrappers.php
similarity index 100%
rename from lib/xmlrpc_wrappers.inc
rename to lib/xmlrpc_wrappers.php

diff --git a/lib/xmlrpcs.inc b/lib/xmlrpcs.php
similarity index 100%
rename from lib/xmlrpcs.inc
rename to lib/xmlrpcs.php