reflect: add support for linked lists

Linked lists are usually implemented as follows:

    type linkedList struct {
        next *linkedList
        data int // whatever
    }

This caused a stack overflow while writing out the reflect run-time type
information. This has now been fixed by splitting the allocation of a
named type number from setting the underlying type in the sidetable.

src/reflect/sidetables.go

@@ -5,10 +5,10 @@ import (
 )
 
 // This stores a varint for each named type. Named types are identified by their
-// name instead of by their type. The named types stored in this struct are the
-// simpler non-basic types: pointer, struct, and channel.
+// name instead of by their type. The named types stored in this struct are
+// non-basic types: pointer, struct, and channel.
 //go:extern reflect.namedNonBasicTypesSidetable
-var namedNonBasicTypesSidetable byte
+var namedNonBasicTypesSidetable uintptr
 
 //go:extern reflect.structTypesSidetable
 var structTypesSidetable byte