Add batch script for running nightly on windows.

After much trial and error, this script seems to work on windows. The actual
cygwin command is a little messy, but it does work in our headless testing
environment.

Also, update common.bash to reuse CHPL_NIGHTLY_LOGDIR variable when it is
already set in the environment.

git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@23853 3a8e244f-b0f2-452b-bcba-4c88e055c3ca
reverting r23779

r23779 turned off work stealing by default for qthreads to test the performance
impact. It did not have the desired impact (meaning multithreaded schedulers
have additional overhead beyond the work stealing routines) so I'm removing it.


git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@23854 3a8e244f-b0f2-452b-bcba-4c88e055c3ca