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

[Alexey Samsonov]

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. This change is fine for now, though. We will be able to implement correct accessors and/or introduce DWARFUnitSection::parse() function later as needed.

Thanks!

http://reviews.llvm.org/D5310