Miscellaneous Fixes for SparseBitVector

Summary:

1. Fix return value in `SparseBitVector::operator&=`.
2. Add checks if SBV is being assigned is invoking SBV.

Reviewers: dberlin

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D11342

Committed on behalf of sl@

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242693 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed