Updated Clock class interface.
Added pointer to the class descriptor argument, that permits
to implement more complex clock classes, in some ways similar to templates.
Updated LPC13xx clock classes.
Fixed base GpTimer init.
Updated clocking system of LPC13xx.
Common parts of USB PLL and System PLL configuration
moved to a separate functions.
Updated clock system of LPC11xx and LPC11Exx.
Updated coding style in clock drivers.
Added clock subsystem functions for LPC43xx.
Updated UART clock calculation for LPC43xx.
UART clock is calculated from the peripheral clock using new clock system.