Added peek() function to ringbuffer
Set timer mach interrupt to disabled by default
Implementing new way to set hook functions from interrupt routines.

This may allow running of tasks from lower priority interrupts or
thread mode hanlders.
Set interrupt priorities so that UART may preempt SysTick.

This allows lower priority handlers to be run from Systick interrupt.
Modifications to interrupt handling.

Added low priority event loop handling in TIM14 interrupt.
Removed all timer prescalers, seems to work now.
Modified systick to use counter and modified wait_ms() to use this counter.
Set Systick priority higer.
Improved GSM pattern waiting and interrupt processing.
Added new flags that follows modem state