[ASan] Handle SIGBUS on Linux.

Summary:
On Linux in some situations we can get SIGBUS instead of SIGSEGV on
stack overflow, so asan should handle SIGBUS as well as SIGSEGV.

https://code.google.com/p/address-sanitizer/issues/detail?id=369

Reviewers: samsonov, glider

Reviewed By: glider

Subscribers: glider, llvm-commits

Differential Revision: http://reviews.llvm.org/D6923

llvm-svn: 225630