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

src/reflect/type.go

@@ -163,7 +163,7 @@ func (t Type) stripPrefix() Type {
 	if (t>>4)%2 != 0 {
 		// This is a named type. The data is stored in a sidetable.
 		namedTypeNum := t >> 5
-		n, _ := readVarint(unsafe.Pointer(uintptr(unsafe.Pointer(&namedNonBasicTypesSidetable)) + uintptr(namedTypeNum)))
+		n := *(*uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(&namedNonBasicTypesSidetable)) + uintptr(namedTypeNum)*unsafe.Sizeof(uintptr(0))))
 		return Type(n)
 	}
 	// Not a named type, so the value is stored directly in the type code.