annotate overloaded private class members where needed

[andrurogerz]

Purpose

Running IDs across the LLVM source, I observed a few cases where private methods that should have been annotated due to being referenced in the same translation unit. In these instances, the missed private methods had overloads and their references were ambiguous. This PR addresses the issue and makes IDS properly flag these methods for export.

Overview

1. Override VisitUnresolvedMemberExpr which gets called in this scenario. Invoke the existing export_function_if_needed for each method declaration the expression may reference. This is only done for private methods because public methods will always be annotated.
2. Add a new test case. For this test force Clang language options to -fno-delayed-template-parsing, which is already the default on Linux and Darwin. This is required on Windows, where the default behavior is -fdelayed-template-parsing to better match MSVC behavior. More details here. Without this argument, the new test case does not pass when run on Windows.

Validation

1. New tests case.
2. Ran tests on Windows and Linux.
3. Manually ran on a subset of the llvm headers and inspected results.