Prevent Cygwin from concealing non-abort() crashes

Prevent Cygwin from concealing non-abort() crashes

BIND system tests are run in a Cygwin environment.  Apparently Cygwin
shell sets the SEM_NOGPFAULTERRORBOX bit in its process error mode which
is then inherited by all spawned child processes.  This bit prevents the
Windows Error Reporting dialog from being displayed, which I assume is
part of an effort to contain memory handling errors triggered by Cygwin
binaries in the Cygwin environment.  Unfortunately, this also prevents
automatic crash dump creation by Windows Error Reporting and Cygwin
itself does not handle memory errors in native Windows processes spawned
from a Cygwin shell.

Fix by clearing the SEM_NOGPFAULTERRORBOX bit inside named if it is
started in a Cygwin environment, thus overriding the Cygwin-set process
error mode in order to enable Windows Error Reporting to handle all
named crashes.