Move PTRACE_GETREGSET and PTRACE_SETREGSET to nat/linux-ptrace.h

Move PTRACE_GETREGSET and PTRACE_SETREGSET to nat/linux-ptrace.h

Macros PTRACE_GETREGSET and PTRACE_SETREGSET are defined locally in
some places in GDB and GDBserver.  This patch is to move them to
nat/linux-ptrace.h to avoid duplication.

gdb:

2015-06-01  Yao Qi  <yao.qi@linaro.org>

	* amd64-linux-nat.c: Include "nat/linux-ptrace.h".
	* i386-linux-nat.c: Likewise.
	* nat/linux-ptrace.h (PTRACE_GETREGSET, PTRACE_SETREGSET): Define.
	* s390-linux-nat.c: Include "nat/linux-ptrace.h".
	(PTRACE_GETREGSET, PTRACE_SETREGSET): Remove.
	* x86-linux-nat.c: Include "nat/linux-ptrace.h".
	* x86-linux-nat.h (PTRACE_GETREGSET, PTRACE_SETREGSET): Remove.

gdb/gdbserver:

2015-06-01  Yao Qi  <yao.qi@linaro.org>

	* linux-s390-low.c (PTRACE_GETREGSET, PTRACE_SETREGSET): Remove.
	* linux-x86-low.c: Likewise.