Added test for xml_parser_set_option

- For skipping white space and triggering invalid encoding value error

ext/xml/tests/xml_parser_set_option_variation4.phpt

@@ -0,0 +1,25 @@
+--TEST--
+xml_parser_free - Test setting skip whitespace and invalid encoding type
+--CREDITS--
+Mark Niebergall <mbniebergall@gmail.com>
+PHP TestFest 2017 - UPHPU
+--SKIPIF--
+<?php
+if (!extension_loaded("xml")) {
+    print "skip - XML extension not loaded";
+}
+?>
+--FILE--
+<?php
+
+$xmlParser = xml_parser_create();
+
+var_dump(xml_parser_set_option($xmlParser, XML_OPTION_SKIP_WHITE, 1));
+var_dump(xml_parser_set_option($xmlParser, XML_OPTION_TARGET_ENCODING, 'Invalid Encoding'));
+
+?>
+--EXPECTF--
+bool(true)
+
+Warning: xml_parser_set_option(): Unsupported target encoding "Invalid Encoding" in %s on line %d
+bool(false)