Remove linux-waitpid.c debugging code

Remove linux-waitpid.c debugging code

The debugging code in linux-waitpid.c is one of the few remaining
spots that depends on the gdb/gdbserver difference.

My first thought was that this code is not extremely useful, so this
patch removes this code.  (However, if it is actually useful to
someone, we could make it work by introducing a new abstraction.)

gdb/ChangeLog
2019-06-11  Tom Tromey  <tom@tromey.com>

	* nat/linux-waitpid.c: Don't include server.h.
	(linux_debug): Remove.
	(my_waitpid): Update.