AArch64: Remove asm/ptrace.h inclusion in sys/user.h and sys/procfs.h

AArch64: Remove asm/ptrace.h inclusion in sys/user.h and sys/procfs.h

This patch fixes an issue observed by the Xen project, where including
signal.h exposes various PSR_MODE #defines.  This is due to the usage
in sys/user.h and sys/procfs.h of the struct user_pt_regs and
user_fpsimd_state included via asm/ptrace.h.  The namespace pollution
this inclusion introduce is already partially fixed with some #undef
of the PTRACE_* symbols, but other symbols like the PSR_MODE ones are
still present, and undefining them is not safe since a user can
include ptrace.h before user.h.

My proposition is to define the 2 structures we need in user.h and get
rid of the asm/ptrace.h inclusion.

Build and make check are clean on AArch64.

2014-05-20  Will Newton  <will.newton@linaro.org>
	    Yvan Roux  <yvan.roux@linaro.org>

	* sysdeps/unix/sysv/linux/aarch64/sys/user.h: Remove unused
	#include of asm/ptrace.h.
	(PTRACE_GET_THREAD_AREA): Remove #undef.
	(PTRACE_GETHBPREGS): Likewise.
	(PTRACE_SETHBPREGS): Likewise.
	(struct user_regs_struct): New structure.
	(struct user_fpsimd_struct): New structure.
	* sysdeps/unix/sysv/linux/aarch64/sys/procfs.h: Remove unused
	#include of asm/ptrace.h and second #include of sys/user.h.
	(PTRACE_GET_THREAD_AREA): Remove #undef.
	(PTRACE_GETHBPREGS): Likewise.
	(PTRACE_SETHBPREGS): Likewise.
	(ELF_NGREG): Use new struct user_regs_struct.
	(elf_fpregset_t): Use new struct user_fpsimd_struct.