Implement support for a new LLVM 1.3 bytecode format, which uses uint's

Implement support for a new LLVM 1.3 bytecode format, which uses uint's
to index into structure types and allows arbitrary 32- and 64-bit integer
types to index into sequential types.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12651 91177308-0d34-0410-b5e6-96231b3b80d8