wait.h: add linux specific, thread-related waitpid() flags
wait.h: add linux specific, thread-related waitpid() flags

these flags are needed in order to be able to handle lwp id's
which the kernel returns after clone() calls for new threads
via ptrace(PTRACE_GETEVENTMSG).

fortunately, they're the same for all archs and in the reserved
namespace.

chardi/musl,chardi/musl,chardi/musl