x11-toolkits/fox17: Fix build on FreeBSD 12.2. pthread_getname_np() was MFC'd
in r362264 and I didn't take into account in the original patch.
FXThread.cpp:970:8: error: no matching function for call to 'pthread_getname_np'
/usr/include/pthread.h:305:6: note: candidate function not viable: no known
conversion from 'const volatile FX::FXThreadID' (aka 'const volatile unsigned
long') to 'pthread_t' (aka 'pthread *') for 1st argument
int pthread_getname_np(pthread_t, char *, size_t);
Reported by: pkg-fallout