[llvm-pdbdump] Support native ordering of subsections in raw mode.

This is the same change for the YAML Output style applied to the
raw output style.  Previously we would queue up all subsections
until every one had been read, and then output them in a pre-
determined order.  This was because some subsections need to be
read first in order to properly dump later subsections.  This
patch allows them to be dumped in the order they appear.

Differential Revision: https://reviews.llvm.org/D34015

llvm-svn: 305034