Basic: whitespace cleanup

Remove unnecessary separation of anonymous namespace.  NFC.
Basic: fix handling for Windows Itanium environment

This corrects the handling for i686-windows-itanium.  This environment is nearly
identical to Windows MSVC, except it uses the itanium ABI for C++.
test: add a test for windows itanium exceptions

Some time ago, I noticed that try would get resolved incorrectly for Windows
Itanium targets.  Add an explicit test to exsure that exceptions are handled
correctly for Windows Itanium environments.