[ORC][examples] Update Kaleidoscope and BuildingAJIT tutorial series to OrcV2.

This patch updates the Kaleidoscope and BuildingAJIT tutorial series (chapter
1-4) to OrcV2. Chapter 5 of the BuildingAJIT series is removed -- it will be
re-instated once we have in-tree support for out-of-process JITing.

This patch only updates the tutorial code, not the text. Patches welcome for
that, otherwise I will try to update it in a few weeks.