Added time conversion utilities in Ar::Time namespace.

- Updated test code to use milliseconds for sleep times.
Made IrqStateSetAndRestore a template class.

- IrqStateSetAndRestore is now a template class that takes the desired
  interrupt mask state as a template argument.
- Created typedefs of IrqStateSetAndRestore for enabling and disabling
  interrupts.
- Using new IrqDisableAndRestore type throughout.
- Added docs for IrqStateSetAndRestore.
Doxygen documentation improvements.

- Using a custom Doxygen XML layout file.
- Turned off generation of file docs.
- Added README.md to input as the mainpage docs.
- Improved ar group docs a bit.
Kernel improvements.

- Changed timeout parameters to be in milliseconds, with the value
  converted internally to ticks.
- Added ThreadToMemberFunction<T> and ThreadToMemberFunctionWithStack<S,T>
  template classes to enable creating a thread whose entry point is
  a member function of an object.
- Moved documentation comment for Kernel::run() to ar_kernel.h.
- Added enterInterrupt() and exitInterrupt() to Kernel class.
- Added InterruptWrapper helper class.
- Updated timeout values passed in test code.
- Changed TestSem1 to use ThreadToMemberFunctionWithStack<S,T>.
Imported core mbed sources.

- These are the original sources, committed unmodified to allow for
  easily identifying changes.
- The only difference from the original is that the hal/cmsis/x files
  have been merged into hal/targets/x. And those CMSIS files that were
  already in src/include/device were not imported.
Using mbed in test project.

- Made a few changes to the mbed code to get things to compile.
- Updated argon_test IAR project to include mbed files.
- Switched IAR project to full C++ and full stdlib.
- Added mbed directories to include paths.
- Switched to 128KB_Pflash.icf linker config.