This removes ptid_get_lwp in favor of calling the ptid_t::lwp method.

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

	* common/ptid.c (ptid_get_lwp): Remove.
	* common/ptid.h (ptid_get_lwp): Don't declare.
	* aarch64-linux-nat.c: Update.
	* ada-tasks.c: Update.
	* aix-thread.c: Update.
	* amd64-linux-nat.c: Update.
	* arm-linux-nat.c: Update.
	* corelow.c: Update.
	* fbsd-nat.c: Update.
	* fbsd-tdep.c: Update.
	* gnu-nat.c: Update.
	* i386-cygwin-tdep.c: Update.
	* i386-gnu-nat.c: Update.
	* i386-linux-nat.c: Update.
	* ia64-linux-nat.c: Update.
	* inf-ptrace.c: Update.
	* infrun.c: Update.
	* linux-fork.c: Update.
	* linux-nat.c: Update.
	* linux-tdep.c: Update.
	* linux-thread-db.c: Update.
	* mips-linux-nat.c: Update.
	* nat/aarch64-linux-hw-point.c: Update.
	* nat/aarch64-linux.c: Update.
	* nat/linux-btrace.c: Update.
	* nat/linux-osdata.c: Update.
	* nat/linux-procfs.c: Update.
	* nat/x86-linux-dregs.c: Update.
	* obsd-nat.c: Update.
	* ppc-fbsd-nat.c: Update.
	* ppc-linux-nat.c: Update.
	* procfs.c: Update.
	* python/py-infthread.c: Update.
	* ravenscar-thread.c: Update.
	* remote.c: Update.
	* s390-linux-nat.c: Update.
	* sol-thread.c: Update.
	* sol2-tdep.c: Update.
	* spu-linux-nat.c: Update.
	* x86-linux-nat.c: Update.
	* xtensa-linux-nat.c: Update.

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

	* linux-low.c: Update.
	* linux-mips-low.c: Update.
	* lynx-low.c: Update.
	* nto-low.c: Update.
	* remote-utils.c: Update.
	* server.c: Update.
	* spu-low.c: Update.
	* target.c: Update.
	* thread-db.c: Update.