lib: do not allocate/free thread funcnames

  This avoids memory heap fragmentation and imposses less load on the
system memory allocator.

* thread.h: FUNCNAME_LEN defined to 64 (ISO C99 says max 63)

Signed-off-by: Jorge Boncompte [DTI2] <jorge@dti2.net>
[changed FUNCNAME_LEN to a less arbitrary value]
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
3 files changed