[llvm-rc] Add ICON and HTML parsing ability (parser, pt 2/8).

This extends the current llvm-rc parser by ICON and HTML resources.
Moreover, some tests have been slightly rewritten.

Thanks for Nico Weber for his original work in this area.

Differential Revision: https://reviews.llvm.org/D36891

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@311939 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed