Add support for the VS2017 built binaries.

There's 2 things that had to be fixed:
- There's a new flag value for the 32 bit offset fixups, we used to always see a flag value of 0 but it's now set to 0x2000 in the VS2017 binaries.
- Add a workaround for what seems to be a toolchain bug in VS2017, the PDB contain some invalid symbols, see https://developercommunity.visualstudio.com/content/problem/47386/invalid-symbols-when-using-rtti.html

With these 2 changes we fully support the VS2017 built binaries.

BUG=chromium:683729

Review-Url: https://codereview.chromium.org/2856933003
3 files changed