[PATCH] Support re-exec of sanitized executable with preloading libasan on Linux

[Yury Gribov]

> OMG, this is very complex and fragile.

The main complexity comes from save-restore the environment which is in turn necessary so that the reexecuted program does not notice that we've changed LD_PRELOAD/ASAN_OPTIONS.

http://reviews.llvm.org/D5931