C++: simple profiling timers

[.. code ...]
IPAACA_SIMPLE_TIMER_BEGIN(blockid1)
[... first code block to time ...]
IPAACA_SIMPLE_TIMER_END(blockid1, "Processing loop 1")
[...]

-> e.g.: "Processing loop - us elapsed: 15" to terminal

Several blocks can be timed in one stack frame using more blockids
(TODO: implement profiling mode that can be turned on/off)