ASACORE:1093 C++ unit tests for about failed to build on OSX with the new about rework

The unit tests could not find operator << function which is a part of String.h as a global
function but not a part of the qcc namespace. The solution was to declare and include String.h
before we include other unit test framework header files

Change-Id: I7c77e8bc50fbadc73ae1eebb38468f2e736cc768
Signed-off-by: Nikhil Dabhade <ndabhade@qce.qualcomm.com>
Merge "ASACORE:1093 C++ unit tests for about failed to build on OSX with the new about rework"