[emb/tp3] Notes on different functions available in linux env
for measuring time used by a process / thread.
[emb/TP3] Benchmark basic execution and printing functions / macros.
[emb/TP3] Updated report with more research on time functions.
[emb/TP3] Tested time functions candidates for benchmarking.
[emb/TP3] Added comment on benchmark limitation.
[emb/TP3] Cleaned up bench.{c,h}.

Removed stuff not related to clock_gettime.
[emb/TP3] Commenting results.
[emb/TP3] Fixed missing parenthesis around macro argument.
[emb/TP3] Replaced bench.h with jlibc bench.h
[emb/TP3] Used semaphores to measure context switches cost.
[emb/TP3] Updated time needed.
[emb/TP3] Used command line arguments to parameterize benchmarks to run.
[emb/TP3] Turned variables into global variables.
[emb/TP3] Added thread context switch measures. Turned everything
in global variable.
[emb/TP3] Added context switches measure results.
[emb/TP3] Updated report.
[emb/TP3] Restored `_exit` call instead of `exit`.
[emb/TP3] Better control with command line: select tests,
be verbose or do not be.
[emb/TP3] Removed extra 's' printed when printing time.
[emb/TP3] Fixed missing includes.