[PATCH] Make getUnitForOffset a DWARFUnit method instead of a DWARFContext method.

[David Blaikie]

>>! In D5310#14, @samsonov wrote:
> LGTM. I'd rather not make DWARFUnitSection inherit from SmallVector -  unit section is not a vector, vector is just a way we represent a set of units, and I'm not sure we want to expose all SmallVector accessors to DWARFUnitSection users.

'spose I should've noticed that, though I didn't. Agreed with your sentiments. :/

The derived template can have a bunch of accessors without exposing them to the other clients.

http://reviews.llvm.org/D5310