After this commit, swift_retain will return no reference and LLVMARCContract pass is modified NOT to rewrite
swift_retain_noresult to old swift_retain which forwarded the reference.
Swift SVN r32075
I asked that the patches were split up so I could do post commit review.
This reverts commit r32059.
This reverts commit r32058.
This reverts commit r32056.
This reverts commit r32055.
Swift SVN r32060
Implement these backstops in the stdlib instead of the runtime, where we can at least interpolate the error value and give a slightly more informative error. Could still be improved by handing the source location down from the point of the crash instead of using the location from the stdlib source. Somewhat addresses rdar://problem/20807523.
Swift SVN r29401
