[codeview] Remove StreamReader copying method.

Since we want to move toward zero-copy access to stream data, we
want to remove all instances of copying operations.  So get rid
of some of those here.

Differential Revision: http://reviews.llvm.org/D20720
Reviewed By: ruiu

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@270960 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed