Add a test for assignment operator behavior which was changed in
r195239, as well as a comment about the fact that assigning over
a moved-from object was in fact tested. Addresses some of the review
feedback on r195239.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195260 91177308-0d34-0410-b5e6-96231b3b80d8
Make the moved-from SmallPtrSet be a valid, empty, small-state object.
Enhance the tests to actually require moves in C++11 mode, in addition
to testing the moved-from state. Further enhance the tests to cover
copy-assignment into a moved-from object and moving a large-state
object. (Note that we can't really test small-state vs. large-state as
that isn't an observable property of the API really.) This should finish
addressing review on r195239.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195261 91177308-0d34-0410-b5e6-96231b3b80d8
CR feedback for r195166: Add comments regarding type unit mapping and type units disabling cross-CU sharing.

Changes suggested by Manman Ren.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195262 91177308-0d34-0410-b5e6-96231b3b80d8
DwarfCompileUnit: Initialize DebugInfoOffset.

While not strictly necessary (the class has an invariant that
"setDebugInfoOffset" is called before "getDebugInfoOffset" - anyone
client that actually gets the default zero offset is buggy/broken) this
is consistent with the code as originally written and the removal of the
initialization was an accident in r195166.

Suggested by Manman Ren.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195263 91177308-0d34-0410-b5e6-96231b3b80d8