Add stub for xmlrpc

Author: shivammathur

extension/BuildPhpExtension/config/stubs/xmlrpc.composer.json

@@ -0,0 +1,13 @@
+{
+  "require": {
+    "libiconv": "*",
+    "libxml2": "*"
+  },
+  "php-ext": {
+    "configure-options": [
+      {
+        "name": "with-xmlrpc"
+      }
+    ]
+  }
+}