Checking in Chris's suggestions:

Checking in Chris's suggestions:
Added assert() to ensure symbol table is well formed.
Added code to remember the value that was found; resolving types can change
the symbol table and invalidate the value of the iterator.
Added comments to the ResolveTypes() function (mainly for my own benefit).
Please feel free to correct the comments if they are not accurate.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@9693 91177308-0d34-0410-b5e6-96231b3b80d8