include/my_pthread.h:
Fix for Bug#27970 "Fix for bug 24507 makes mysql_install_db fail".
Removed macro NPTL_PTHREAD_EXIT_BUG, because it doesn't work in dynamic
environment. One can switch between NPTL and LT on the fly on Linux.
Added pthread_dummy(ESRCH) for those platforms that don't have pthread_kill.
This ensures that there won't be an error in mysqld.cc where the return value
is being checked from the function call.
mysys/my_thr_init.c:
Check for a Linux is enough. There is an additional test if
NPTL is in use before spwaning the extra thread.