Use std::unique_ptr to handle ownership of DwarfUnits in DwarfFile.

So Chandler - how about those range algorithms? (would really love a
dereferencing range adapter for this sort of stuff)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206921 91177308-0d34-0410-b5e6-96231b3b80d8
Change the prototype for MCContext::FatalError() so it can be called
from places like MCCodeEmitter() in the MC backend when the
MCContext is const.

I was going to use this in my change for r206669 but Jim convinced
me to use an assert there. But this still is a good tweak.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206923 91177308-0d34-0410-b5e6-96231b3b80d8
[docs] Add a note to docs/README.txt

Added note to docs/README.txt on how to check the reachibility of
external links in the documentation.

Patch by Dan Liew!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206924 91177308-0d34-0410-b5e6-96231b3b80d8