fix handling VAR vs VAR= in putenv

using _putenv_s eliminates behavior diff in TS/NTS

ext/standard/basic_functions.c

@@ -4148,7 +4148,7 @@ PHP_FUNCTION(putenv)
 		Obviously the CRT version will be useful more often. But
 		generally, doing both brings us on the safe track at least
 		in NTS build. */
-	&& _putenv(pe.putenv_string) == 0
+	&& _putenv_s(pe.key, value ? value : "") == 0
 # endif
 	) { /* success */
 # endif