compiler: fix parsing of composite literals with omitted pointer types
compiler: fix parsing of composite literals with omitted pointer types

The frontend could parse omitted pointer typess at the end of the
type, but not in the middle, so code like []*[][]int{{{1}}} failed.

Test case is in https://golang.org/cl/123477.

Fixes golang/go#26340

Change-Id: I32f0c7154e6525871a5304e92215f4b3a64eac32
Reviewed-on: https://go-review.googlesource.com/123479
Reviewed-by: Than McIntosh <4b2922593166fc595a9b1a408f34f5d3817fe9d2@google.com>

golang/gofrontend,golang/gofrontend,golang/gofrontend,golang/gofrontend