[PATCH] Dead strip atoms with deadStripAlways attribute even if dead strip is not enabled.

[kledzik at apple.com]

  I think deadStripAlways came about when I was surveying ELF, PECOFF, and mach-o to come up with the base set of attributes for all atoms.  I think there was something in PECOFF that seemed to map to deadStripAlways.  If there is not actually any existing format that uses this, we should drop it.

  It is a weird concept because an otherwise dead atom could have a reference to a deadStripAlways atom that keeps it live.  But we are not doing real dead stripping, so we don't know the dead atom is dead, leaving the deadStripAlways atom not dead stripped...

  Regarding linker synthesized atoms, my plan for mach-o was to have the linker generated pseudo file would look like a static library and only synthesize atoms when needed.  So there would be no excess atoms/symbols to dead strip.

http://llvm-reviews.chandlerc.com/D1267