Implement HighResolutionTimer for Posix by using native timers.
Callbacks are triggered with realtime interrupts if they are supported.
Create an enum to track user-defined interrupts as well as an initializer and
handler to register these interrupts per thread.
Add test cases for timers for both single and multiple.
Fix Sleep function to continue sleeping if interrupted by system.
Add local .gdbinit to ignore signal 34 which is used by high res timer
Sandy Carter