Set thread names

[andrey-utkin]

With this change, we can see the purpose of each threads in the debugger, like that:

(gdb) info threads
  Id   Target Id                                      Frame
* 1    Thread 0x7f8ad6aef600 (LWP 3697) "MAIN"        0x00007f8ae02a5adf in __GI___clock_nanosleep (clock_id=clock_id@entry=0, flags=flags@entry=0, req=req@entry=0x7ffebcd3d9d0, rem=rem@entry=0x7ffebcd3d9d0)
    at ../sysdeps/unix/sysv/linux/clock_nanosleep.c:78
  2    Thread 0x7f8acc8da6c0 (LWP 3737) "rcn2"        0x00007f8ae0251d71 in __futex_abstimed_wait_common64 (private=32650, cancel=true, abstime=0x0, op=393, expected=0, futex_word=0x7f8ac0057680)
    at ./nptl/futex-internal.c:57
  3    Thread 0x7f8acdffb6c0 (LWP 3730) "dev2"        0x00007f8ae02d44cd in __GI___poll (fds=fds@entry=0x7f8acdfeeda0, nfds=nfds@entry=1, timeout=timeout@entry=100) at ../sysdeps/unix/sysv/linux/poll.c:29
  4    Thread 0x7f8ace7fc6c0 (LWP 3729) "dev1"        0x00007f8ae02a5adf in __GI___clock_nanosleep (clock_id=clock_id@entry=0, flags=flags@entry=0, req=req@entry=0x7f8ace7fad50, rem=rem@entry=0x7f8ace7fad50)
    at ../sysdeps/unix/sysv/linux/clock_nanosleep.c:78
  5    Thread 0x7f8aceffd6c0 (LWP 3711) "LICENSE"     0x00007f8ae02a5adf in __GI___clock_nanosleep (clock_id=clock_id@entry=0, flags=flags@entry=0, req=req@entry=0x7f8aceffbf90, rem=rem@entry=0x7f8aceffbf90)
    at ../sysdeps/unix/sysv/linux/clock_nanosleep.c:78
  6    Thread 0x7f8acf7fe6c0 (LWP 3710) "RTSP_SERVER" 0x00007f8ae02d44cd in __GI___poll (fds=0x563a41ddfda8, nfds=2, timeout=100) at ../sysdeps/unix/sysv/linux/poll.c:29
  7    Thread 0x7f8ad48246c0 (LWP 3705) "HLS_SERVER"  0x00007f8ae02e3042 in epoll_wait (epfd=13, events=0x7f8ad4825010, maxevents=120000, timeout=100) at ../sysdeps/unix/sysv/linux/epoll_wait.c:30
  8    Thread 0x7f8ad51856c0 (LWP 3704) "API"         0x00007f8ae02e3042 in epoll_wait (epfd=7, events=0x7f8ad5186010, maxevents=120000, timeout=100) at ../sysdeps/unix/sysv/linux/epoll_wait.c:30
  9    Thread 0x7f8ad5ae66c0 (LWP 3703) "MONITORING"  0x00007f8ae02a5adf in __GI___clock_nanosleep (clock_id=clock_id@entry=0, flags=flags@entry=0, req=req@entry=0x7f8ad5ae4fa0, rem=rem@entry=0x7f8ad5ae4fa0)
    at ../sysdeps/unix/sysv/linux/clock_nanosleep.c:78
  10   Thread 0x7f8ad62e76c0 (LWP 3702) "TRIGGER"     0x00007f8ae02d44cd in __GI___poll (fds=fds@entry=0x7f8ad62e5f48, nfds=nfds@entry=1, timeout=timeout@entry=100) at ../sysdeps/unix/sysv/linux/poll.c:29
  11   Thread 0x7f8ad6ae86c0 (LWP 3701) "STATUS"      0x00007f8ae02d44cd in __GI___poll (fds=fds@entry=0x7f8ad6ae6f48, nfds=nfds@entry=1, timeout=timeout@entry=100) at ../sysdeps/unix/sysv/linux/poll.c:29