For PR351:

For PR351:
Generally, remove use of fork/exec from bugpoint in favor of the portable
sys::Program::ExecuteAndWait method. This change requires two new options
to bugpoint to tell it that it is running in "child" mode. In this mode,
it reads its input and runs the passes. The result code signals to the
parent instance of bugpoint what happened (success, fail, crash).

This change should make bugpoint usable on Win32 systems.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24961 91177308-0d34-0410-b5e6-96231b3b80d8