Fix posix.fork1() / os.fork1() to only call PyOS_AfterFork() in the child process rather than both parent and child.
Fix posix.fork1() / os.fork1() to only call PyOS_AfterFork() in the child
process rather than both parent and child.

Does anyone actually use fork1()?  It appears to be a Solaris thing
but if Python is built with pthreads on Solaris, fork1() and fork()
should be the same.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator