[PATCH] Initial DWARF64 support for .debug_line

[Ed Maste]

It just fell off my radar during the previous iterations.  I subsequently committed an improved version of the change to LLDB - that's in http://llvm-reviews.chandlerc.com/D2007 .

We'll want the equivalent change here too, but I think it makes sense to bring in this by itself since it's already done.  It wasn't a trivial rebase against head so I'll commit if I can get a review of the new diff.

http://reviews.llvm.org/D1988