ifpps: Optionally display median values for CPU load and interrupts

Using the -m/--median command line option, median values across all CPUs
are displayed for CPU load, interrupts per interval, sw interrupts per
interval and absolute number of interrupts.

Also update the manpage accordingly.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
ifpps: Update usage with respect to median values

This was missing in commit 971b1d95 ("ifpps: Optionally display median
values for CPU load and interrupts"). Update the usage to reflect the
changes too.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
gitignore: add config.log file to git ignore

Ignore the config.log file in Git as this is automatically generated.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
ifpps: median: add whitespace padding in one occurence

Add whitespace padding in one occurence of 'med:' output.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
ifpps: Consistently list command line options

Instead of (more or less) arbitrarily listing the command line options,
sort them according to the following rule:

- options with required argument, alphabetically by short option
- options without argument, alphabetically by short option
- common options -v/--version and -h/--help

Do this in the short options string, the long options struct, the
in-program usage and the man page.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>