Remove the Copied parameter from MemoryObject::readBytes.

There was exactly one caller using this API right, the others were relying on
specific behavior of the default implementation. Since it's too hard to use it
right just remove it and standardize on the default behavior.

Defines away PR16132.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182636 91177308-0d34-0410-b5e6-96231b3b80d8