This patch replaces SmallSet<T *, N> with SmallPtrSet<T *, N>. Note
that SmallSet.h "redirects" SmallSet to SmallPtrSet for pointer
element types:
template <typename PointeeType, unsigned N>
class SmallSet<PointeeType*, N> : public SmallPtrSet<PointeeType*, N>
{};
We only have 10 instances that rely on this "redirection", with more
than half of them under clang-tools-extra/. Since the redirection
doesn't improve readability, this patch replaces SmallSet with
SmallPtrSet for pointer element types.
I'm planning to remove the redirection eventually.
ccd5ddab9b