Fix resolution of certain recursive types.

Summary:
If a struct type S has a member T that has a member that is a function that
returns a typedef of S* the respective field would be duplicated, which caused
an assert down the line in RecordLayoutBuilder. This patch adds a check that
removes the possibility of trying to resolve the same type twice within the
same callstack.

This commit also adds unit tests for these failures.

Fixes https://llvm.org/bugs/show_bug.cgi?id=20486.

Patch by Cristian Hancila.

Test Plan: Run unit tests.

Reviewers: clayborg spyffe

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D8561

llvm-svn: 234441