Update (doxygen) comments
New flow option -I for one-way delay calculation

Revert patch 61b4096aea. Instead display delay calculation only if option
-I is given. Make the same with RTT calculation (option -A)
Typo in usage_trafgenopt()
Move option -G to the logical right place in switch statement
To avoid code duplication, 'progname' is no more static.

Instead a function set_progname() is defined, which set the program
name based on argv[0]
Make includes explicit
Doxygen doesn't parse static variables or functions in header files

Move all static variables and functions from the header files to the
source files
Update (doxygen) comments
Coding style
Update TODO
likely() and unlikely() macros
Definition of a common error-reporting function

The function outputs to stderr the program name, a colon and a space, a fixed
error message based on the error level, and a second colon and a space followed
by the error message. If errnum is nonzero, a third colon and a space followed
by the string given by strerror(errnum) is printed
flowgrind.c - use common error-reporting function instead of fprintf(stderr, ...)
flowgrindd.c - use common error-reporting function instead of fprintf(stderr, ...)
flowgrind_stop.c - use common error-reporting function instead of fprintf(stderr, ...)
log.c - use common error-reporting function instead of fprintf(stderr, ...)
Functional split up of common.[h|c]

Inspired by GNU's coreutils , don't write a common 'util.c' file with
common definitions and utility routines, since it is most likely the file
get huge over the time and all the functionality is mixed up. Instead write
small files with clear defined purposes: error.[h|c]; progname.[h|c], ...
Fix gcc warnings
Change return value from gettime()

gettime() return nows the return value from system call clock_gettime()
instead the clock resolution
Add gcc attribute 'format' for error function