When marking the declarations in a default argument expression as

When marking the declarations in a default argument expression as
"used", at the time that the default argument itself is used, also
mark destructors that will be called by this expression. This fixes a
regression that I introduced in r113700, which broke WebKit, and fixes
<rdar://problem/8427926>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@113883 91177308-0d34-0410-b5e6-96231b3b80d8