Count all intercepted allocations/deallocations in order to build a small leak-checker.

Count all intercepted allocations/deallocations in order to build a small leak-checker.
This allows to check for leaks, but also to provide debug information on the involved buffers (file, line, size) when a crash happens
todo: evaluate memory cost and slowdown for real apps (disabled by default, needs --cfg=smpi/display-allocs or -analyze flag to be activated)