Temporarily revert r231726 and r231724 as they're breaking the build.:

Author: Lang Hames <lhames@gmail.com>
Date:   Mon Mar 9 23:51:09 2015 +0000

    [Orc][MCJIT][RuntimeDyld] Add header that was accidentally left out of r231724.

Author: Lang Hames <lhames@gmail.com>
Date:   Mon Mar 9 23:44:13 2015 +0000

    [Orc][MCJIT][RuntimeDyld] Add symbol flags to symbols in RuntimeDyld. Thread the
    new types through MCJIT and Orc.

    In particular, add a 'weak' flag. When plumbed through RTDyldMemoryManager, this
    will allow us to distinguish between weak and strong definitions and find the
    right ones during symbol resolution.

llvm-svn: 231731