IOT-1583: Preparing SConscripts for /W3 and /WX changes.

IOT-1583: Preparing SConscripts for /W3 and /WX changes.

Initial commit making changes and small clean-up in SConscript
files to enable adding /W3 and /WX compiler options limited
to the resource/csdk/stack/ directory.

Changes made:
1. Building of stack's code moved to resource/csdk/stack/SConscript.
2. Turned extlibs/timer/ into a static lib, so that it doesn't compile
(and generate warnings) along with other modules' code.

Change-Id: I6c64916dbcfd23edb546d43db7b2470100528baa
Signed-off-by: Pawel Winogrodzki <pawelwi@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/16975
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Dan Mihai <Daniel.Mihai@microsoft.com>