* Re-use existing settings/dk.mk to tunnel ENABLE_DEBUG into the SDK.  Turns out
  this was explicitly included in ~all examples Makefiles, but only after
  settings.mk where it is now used, so include it in settings.mk now and dropped
  it from all the exmaples Makefiles.

* The old settings.mk was apparently confused with using /MT ("link with
  LIBCMT.LIB") on cl command line and /MD ("link with MSVCRT.LIB") on link
  command line (where it was ignored), and you apparently can't pass both
  together to cl, so I settled on /MD (resp. /MDd) now and dropped /MT (resp.
  /MTd).  No idea if that is exactly right, however.

* Introduced client-facing LIBO_SDK_LDFLAGS_STDLIBS that covers kernel32.lib and
  msvcrt.lib vs. msvcrtd.lib on Windows.  Adapted examples Makefiles and
  /ure/source/uretest/Makefile accordingly.  Some examples Makefiles
  additionally use msvcprt.lib, no idea whether that still needs to be
  addressed.

Change-Id: Ia8d9d177e415abfbaf6f9fa6239f0ef9998868be