Recognize Android NDK 8d

Change-Id: I897c88fc9ad548b4164e0f91fea6c25b0be46ee2
ALLJOYN-1711 BusAttachment.enableConcurrentCallbacks added to C bindings

The following functions have been added to the C bindings
alljoyn_busattachment_create_concurrency
    as a general rule a user will not change the default setting for
    concurrency. I chose to make a different function call for when
    the user really does want to change the concurrency.
alljoyn_busattachment_getconcurrency
alljoyn_busattachment_getconnetspec
alljoyn_busattachment_enableconcurrentcallbacks

At least one unit test added for each function binding.  To verify
the binding was functioning as expected.

Small changes made to SConscript to address unusual build failures
sometimes seen when doing a multi-core build.

Change-Id: Ib02285c721b7e70268bb51f421d33f3e7290ae53