Fix for new cygwin 'uname' behavior

In a recent cygwin version, it seems that uname has started returning strings
like 'CYGWIN_NT-6.1-WOW64' rather than simply 'CYGWIN'.  This commit changes
the 'chpl_platform.py' script to change any uname[0] values that start with
'cygwin' to simply 'cygwin'.  We don't currently have any need (that we're
aware of) to distinguish between different windows versions, so this seems
reasonable.

If we do need to do so in the future, we could preserve the uname string
(which was the old behavior) and then change checks against 'cygwin' to check
for 'cygwin*' in other places (like chpl_make.py).






git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@23678 3a8e244f-b0f2-452b-bcba-4c88e055c3ca
Remove setting QT_GUARD_PAGES and QT_WORKER_UNIT from common-qthreads

[ok'd by locale model team]

common-qthreads is sourced for nightly qthreads testing. It should be testing
the "default" configurations but we currently set QT_GUARD_PAGES=true and
QT_WORKER_UNIT=core. It happens that guard_pages are on by default and the
default worker unit is core so these have no real affect as we are just
re-setting part of the default ocnfiguration, but it makes sense to remove them
anyways. They were originally set because the default worker unit wasn't core,
and we wanted to be explicit about setting guard pages, but they are not
needed.


git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@23679 3a8e244f-b0f2-452b-bcba-4c88e055c3ca