Pass an FFI pointer into NFI

Author: chrisseaton

lib/truffle/truffle/fiddle_backend.rb

@@ -78,7 +78,7 @@ def self.convert_ruby_to_native(type, val)
 
   def self.get_pointer_value(val)
     if val.is_a?(String)
-      Truffle::CExt.string_pointer_to_native(val)
+      Truffle::CExt.string_to_pointer(val)
     elsif val.is_a?(Fiddle::Pointer)
       val.to_i
     elsif val.respond_to?(:to_ptr)