build system (v0), add long options, corrections

• mojitos now supports long options, via "optparse.h", written by wellons@nullprogram.com and released into the public domain
• one can choose which captor to include or exclude in the final binary with configure.sh.
• makefile is now POSIX compliant (or at least, should be).
• one now have to fill in the "struct optparse_long" and "struct captor" structs when adding a new captor.
• defined a hard limit to the numbers of fixed options (10), and to the amount of captors (20). These can be changed by modifying NB_MAX_OPTS and NB_MAX_CAPTORS, respectively.
• mojitos now includes "captors.h", generated by the configure.sh script
• changed the signature of add_source() to: void add_source(struct captor*, char*)
• main() now must call the init_captors() function.

doc/mojitos.pre.1

+.Dd January 9, 2023
+.Dt MOJITOS 1
+.Os
+.Sh NAME
+.Nm mojitos
+.Nd An open source system monitoring tool.
+.Sh SYNOPSIS
+.Nm mojitos
+.Op Ar OPTIONS
+.Op Ar SENSOR ...
+.Op Fl e Ar cmd ...
+.Sh DESCRIPTION
+.Nm
+is a monitoring tool with a multitude of sensors that does measurements at the OS level.
+.Nm
+runs on GNU/Linux.
+USAGE
+.Sh EXIT STATUS
+.Ex
+.Sh EXAMPLES
+RAPL values during 2 seconds with a frequency of 2Hz:
+.Bd -literal -offset indent
+$ mojitos -t 2 -f 2 -r
+#timestamp package-00 core0 dram0
+1036389.135659868 10986 2869 1526
+1036389.500183551 1291440 255736 515562
+1036390.000754048 1333553 228393 689513
+1036390.500113978 1581967 267944 701536
+.Ed
+.Pp
+Performance counters (cpu_cycle, cache_ll_r_a and page_faults) during 4 seconds
+with a frequency of 1Hz.
+In the context of cache performance counters (as with "cache_ll_r_a"),
+ _r and _w suffixes mean respectively read and write,
+while the _a, _m and _p ones mean respectively access, miss and pending.
+.Pp
+.Bd -literal -offset indent
+$ ./mojitos -t 4 -f 1 -p cpu_cycles,cache_ll_r_a,page_faults
+#timestamp cpu_cycles cache_ll page_faults
+1036846.351749455 571199 1232 0
+1036847.001098880 348173344 2451387 872
+1036848.000166158 388112961 2509305 791
+1036849.000191883 402255979 2625283 799
+.Ed
+.Pp
+Network values with no time limit with a frequency of 1Hz.
+rxp and txp are the number of received and sent packets, while rxb and txp are
+the number of received and sent bytes.
+.Pp
+.Bd -literal -offset indent
+$ ./mojitos -t 0 -f 1 -d enp0s25
+#timestamp rxp rxb txp txb
+1036559.277376027 0 0 0 0
+1036560.000161101 4 581 2 179
+1036561.000083968 178 268675 55 4954
+1036562.000076162 11 1010 5 510
+1036563.000069724 17 1643 12 3602
+1036564.000113394 990 1493008 369 27299
+.Ed
+.Pp
+overhead of the monitoring when using RAPL and the cpu_cycle performance counter:
+.Pp
+.Bd -literal -offset indent
+$ ./mojitos -t 5 -f 1 -p cpu_cycles -r -s
+#timestamp cpu_cycles package-00 core0 dram0 overhead
+1036988.197227391 162214 19898 4944 1586 149612
+1036989.000151326 332613664 2513116 379577 1115171 739573
+1036990.000116433 482150700 3321341 587218 1380673 315719
+1036991.000182835 525984292 3592582 691221 1385982 272182
+1036992.000165117 397678789 2770561 444030 1375729 510379
+.Ed
+.Sh SEE ALSO
+.Xr perf 1 ,
+.Xr lscpu 1 ,
+.Xr sysfs 5 ,
+.Xr proc 5
+.Sh LICENSE
+MojitO/S is published under the GPL3 license and is part of the
+.Lk https://www.irit.fr/energumen/ [Energumen Project]
+.Sh BUGS
+Yes.