Simplify code a bit by passing StreamFile to the BitstreamCursor constructor.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@221784 91177308-0d34-0410-b5e6-96231b3b80d8
Update for llvm api change.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@221786 91177308-0d34-0410-b5e6-96231b3b80d8