compiler: pass correct 'function' flag to circular_pointer_type

The code in Named_type::do_get_backend was not passing the correct
flag value for circular function types to Backend::circular_pointer_type
(it was always setting this flag to false). Pass a true value if the
type being converted is a function type.

Change-Id: I3255599d30e30ae657ded853526d90a9537c2c22
Reviewed-on: https://go-review.googlesource.com/49330
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
1 file changed