* Change MBED_ASSERTS() to return valid error code, so that
checks are not bypassed on release builds.
* Fix starting address calculations so that "addr" parameter is always
relative to SlicingDevice and "_start" is only added when calls to
underlying storage block is made.
* Bypass BlockDevice:is_valid_*() to underlying block device.
Slicingblockdevice was just verifying addresses independently, without
verifying those from underlying block storage.
Due to discovery of inconsistent sector sizes in devices storage the is_valid_erase function was adjusted,
For FlashIAPBD the 'code size' was included to the calculation, preventing faulty "virtual" addresses calculation.
For SlicingBD the same error was fixed and in all 3 validation functions that sent addresses for validation and program/read/erase
different addresses.
Adding new modules inside the namespace could be breaking change for existing code base
hence add `using namespace::class` for classes newly added to mbed namespace to maintian
backwards compatibility.
MBED_NO_GLOBAL_USING_DIRECTIVE is added to remove auto-addition of namespace
Macro guard `MBED_NO_GLOBAL_USING_DIRECTIVE` is added around namespace, to avoid
polluting users namespace.
Seppo Takalo
Amir Cohen
Yossi Levy
deepikabhavnani