Updated core and platform includes.
Added common include files for cores and platforms.
SdioSpi class moved to platform directory.
Changed include guards naming.
Updated GpTimer and SysTick classes.
Fixed CAS operation in Set Descriptor functions.
Fixed resetting of descriptor with Compare and Swap function.
In previous version descriptors could not be reset due to pointer
values mismatch.
Added CAS emulation for Cortex-M0.
Improved const correctness.