This patch changes flowgrind's timer management to achieve a nanosecond
resolution (precision). In particular, it changes

* the use of gettimeofday() to clock_gettime(). POSIX.1-2008 marks
  gettimeofday() as obsolete
* any use of the 'timeval' struct to the 'timespec' struct
* the use of the select() call to pselect() call
* the use of ctime() to strftime(). POSIX.1-2008 marks ctime() as
  obsolete
Unnecessary include
Change signature of ctimespec_r
Define NSEC_PER_SEC and use it
Not need to normalize here...
Change ordering in fg_time[h|c] since normalize_tp is only called in
time_add
Use 'timespec' struct also in debug.[h|c] so achieve also here a
nanosecond precision
Update NEWS
Update inline comment
Merge pull request #16 from alexander-zimmermann/master

This series of patches changes flowgrind's timer management to achieve a nanosecond precision