win32: Manually generate manifest to indicate Win7 compatibility

Telling Windows that we support Windows 7 means it will stop catching
unhandled exceptions that occur in a callback from kernel mode, and
allow our own crash handler to catch then.
win32: Disable callback crash filter on Vista

We're already disabling that filter on Windows 7 and up using the
application manifest, but Vista doesn't know about Windows 7
compatibility. Turn off the filter on Vista as well.
win32: Dump crashes to UserDataPath instead of cwd (#996)

The working directory on windows is very likely to be the directory of
the binary itself. If we've installed to Program Files, that means we
cannot actually write there. That means we have to find a better place
to write dumps, and the user directory is a better place.