Remove unusual use of using.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@210081 91177308-0d34-0410-b5e6-96231b3b80d8
Use range-based for loop.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@210082 91177308-0d34-0410-b5e6-96231b3b80d8
No need to compute valBit until mask bit is 1.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@210084 91177308-0d34-0410-b5e6-96231b3b80d8
Use auto for obvious types.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@210085 91177308-0d34-0410-b5e6-96231b3b80d8