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.
AArch64: Fix handling of nocancel syscall failures

The current code for nocancel syscalls does not do a comparison of
the system call return value. This leads to code being generated
where the b.cs follows the svc instruction directly without setting
the flags on which the branch depends.

ChangeLog:

2014-05-20  Will Newton  <will.newton@linaro.org>

	* sysdeps/unix/sysv/linux/aarch64/nptl/sysdep-cancel.h (PSEUDO):
	Test the return value of the system call in the nocancel case.