Update nativecall.pod

Describe how to pass allocated pointers to native types in native calls

Author: salortiz

doc/Language/nativecall.pod

@@ -97,14 +97,21 @@ For string arguments that are specified as C<const char *> it is necessary
 to tell Perl not to free the memory allocated to the C string after the
 function returns using C<explicitly-manage> :
 
-    # C prototype is set_foo(const char * foo)
+    # C prototype is void set_foo(const char * foo)
 	sub set_foo(Str) is native('foo') { * }
     my $string = "FOO";
     explicitly-manage($string);
     set_foo($string);
     
 =head1 Basic use of Pointers
 
+When the signature of your native function needs a pointer to some native type
+(int, uint, etc.) all you need to do is declare the argument C<is rw> :
+
+   # C prototype is void my_version(int *mayor, int *minor)
+       sub my_version(int32 is rw, int32 is rw) is native('foo') { * }
+   my_version(my int32 $mayor, my int32 $minor); # Pass a pointer to
+   
 Sometimes you need to get a pointer (for example, a library handle) back from a
 C library. You don't care about what it points to - you just need to keep hold
 of it. The Pointer type provides for this.