Remove ptid_get_tid

Remove ptid_get_tid

This removes ptid_get_tid in favor of calling the ptid_t::tid method.

gdb/ChangeLog
2018-07-03  Tom Tromey  <tom@tromey.com>

	* common/ptid.c (ptid_get_tid): Remove.
	* common/ptid.h (ptid_get_tid): Don't declare.
	* ada-tasks.c: Update.
	* aix-thread.c: Update.
	* bsd-uthread.c: Update.
	* darwin-nat.c: Update.
	* fbsd-nat.c: Update.
	* i386-darwin-nat.c: Update.
	* infrun.c: Update.
	* linux-tdep.c: Update.
	* nto-procfs.c: Update.
	* ppc-ravenscar-thread.c: Update.
	* python/py-infthread.c: Update.
	* ravenscar-thread.c: Update.
	* sol-thread.c: Update.
	* sparc-ravenscar-thread.c: Update.
	* windows-nat.c: Update.

gdb/gdbserver/ChangeLog
2018-07-03  Tom Tromey  <tom@tromey.com>

	* target.c: Update.