Currently there are two issues which prevent building Mbed OS with
-std=gnu++11 when using Arm Compiler 6:
* NanostackRfPhys2lp.cpp contains a narrowing conversion in a braced
initializer list
* ns_types.h includes <stdalign.h> which Arm Compiler 6 currently
does not provide
This patch fixes both issues. The first one is fixed by changing the
underlying type of the corresponding enumeration when the code is
compiled as C++11. The second issue is worked around by avoiding the
use of <stdalign.h> header for Arm Compiler versions prior to 6.12.
Mikhail Maltsev
Jarkko Paso