Automatically detect C++11 flags for supported compilers.

Automatically detect C++11 flags for supported compilers.

This patch set allows the required C++11 command line flags to
be automatically set earlier in the build process.  Currently
only gcc is supported, but adding support for other compilers
is straightforward.  Furthermore, changes are for the most part
isolated to the new `iotivityconfig' python package.  There should
be no need to update SConscript files found throughout the
iotivity source tree.

Change-Id: I4ba0f6712e4a56a1a97630e511e9aabfdcd9e349
Signed-off-by: Ossama <ossama.othman@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/240
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Erich Keane <erich.keane@intel.com>
Reviewed-by: Patrick Lankswert <patrick.lankswert@intel.com>