Condition some sys/ucontext.h contents on __USE_MISC (bug 21457).

Condition some sys/ucontext.h contents on __USE_MISC (bug 21457).

Continuing the fixes for namespace issues arising from sys/ucontext.h,
this patch conditions various definitions, that are not needed for
defining mcontext_t / ucontext_t, on __USE_MISC, so they do not appear
in strict POSIX modes.

This patch is non-exhaustive; that is, it only conditions
straightforward cases and there may be more such definitions that can
be conditioned for these and other architectures, to be dealt with
later in separate patches.  Also, using __USE_MISC is the minimum
change for these definitions where they conflict with POSIX; some
headers already have __USE_GNU conditionals on similar definitions of
names for registers.  The patch specifically does not do anything with
definitions in bits/sigcontext.h, and nor does it condition any
inclusions of bits/sigcontext.h even where in fact that is not needed
on some architectures for the definitions of mcontext_t / ucontext_t.

As other namespace issues in these headers remain, this patch does not
fix bug 21457, nor allow any XFAILs to be removed.

Tested with build-many-glibcs.py.

	[BZ #21457]
	* sysdeps/arm/sys/ucontext.h (R0): Condition on [__USE_MISC].
	(R1): Likewise.
	(R2): Likewise.
	(R3): Likewise.
	(R4): Likewise.
	(R5): Likewise.
	(R6): Likewise.
	(R7): Likewise.
	(R8): Likewise.
	(R9): Likewise.
	(R10): Likewise.
	(R11): Likewise.
	(R12): Likewise.
	(R13): Likewise.
	(R14): Likewise.
	(R15): Likewise.
	* sysdeps/i386/sys/ucontext.h (REG_GS): Likewise.
	(REG_FS): Likewise.
	(REG_ES): Likewise.
	(REG_DS): Likewise.
	(REG_EDI): Likewise.
	(REG_ESI): Likewise.
	(REG_EBP): Likewise.
	(REG_ESP): Likewise.
	(REG_EBX): Likewise.
	(REG_EDX): Likewise.
	(REG_ECX): Likewise.
	(REG_EAX): Likewise.
	(REG_TRAPNO): Likewise.
	(REG_ERR): Likewise.
	(REG_EIP): Likewise.
	(REG_CS): Likewise.
	(REG_EFL): Likewise.
	(REG_UESP): Likewise.
	(REG_SS): Likewise.
	* sysdeps/m68k/sys/ucontext.h (R_D0): Likewise.
	(R_D1): Likewise.
	(R_D2): Likewise.
	(R_D3): Likewise.
	(R_D4): Likewise.
	(R_D5): Likewise.
	(R_D6): Likewise.
	(R_D7): Likewise.
	(R_A0): Likewise.
	(R_A1): Likewise.
	(R_A2): Likewise.
	(R_A3): Likewise.
	(R_A4): Likewise.
	(R_A5): Likewise.
	(R_A6): Likewise.
	(R_A7): Likewise.
	(R_SP): Likewise.
	(R_PC): Likewise.
	(R_PS): Likewise.
	(fpregset_t): Likewise.
	(MCONTEXT_VERSION): Likewise.
	* sysdeps/mips/sys/ucontext.h (CTX_R0): Likewise.
	(CTX_AT): Likewise.
	(CTX_V0): Likewise.
	(CTX_V1): Likewise.
	(CTX_A0): Likewise.
	(CTX_A1): Likewise.
	(CTX_A2): Likewise.
	(CTX_A3): Likewise.
	(CTX_T0): Likewise.
	(CTX_T1): Likewise.
	(CTX_T2): Likewise.
	(CTX_T3): Likewise.
	(CTX_T4): Likewise.
	(CTX_T5): Likewise.
	(CTX_T6): Likewise.
	(CTX_T7): Likewise.
	(CTX_S0): Likewise.
	(CTX_S1): Likewise.
	(CTX_S2): Likewise.
	(CTX_S3): Likewise.
	(CTX_S4): Likewise.
	(CTX_S5): Likewise.
	(CTX_S6): Likewise.
	(CTX_S7): Likewise.
	(CTX_T8): Likewise.
	(CTX_T9): Likewise.
	(CTX_K0): Likewise.
	(CTX_K1): Likewise.
	(CTX_GP): Likewise.
	(CTX_SP): Likewise.
	(CTX_S8): Likewise.
	(CTX_RA): Likewise.
	(CTX_MDLO): Likewise.
	(CTX_MDHI): Likewise.
	(CTX_CAUSE): Likewise.
	(CTX_EPC): Likewise.
	* sysdeps/unix/sysv/linux/aarch64/sys/ucontext.h: Condition
	inclusion of <sys/procfs.h> on [__USE_MISC].
	(greg_t): Condition on [__USE_MISC].
	(gregset_t): Likewise.
	(fpregset_t): Likewise.
	* sysdeps/unix/sysv/linux/arm/sys/ucontext.h (greg_t): Likewise.
	(NGREG): Likewise.
	(gregset_t): Likewise.
	(REG_R0): Likewise.
	(REG_R1): Likewise.
	(REG_R2): Likewise.
	(REG_R3): Likewise.
	(REG_R4): Likewise.
	(REG_R5): Likewise.
	(REG_R6): Likewise.
	(REG_R7): Likewise.
	(REG_R8): Likewise.
	(REG_R9): Likewise.
	(REG_R10): Likewise.
	(REG_R11): Likewise.
	(REG_R12): Likewise.
	(REG_R13): Likewise.
	(REG_R14): Likewise.
	(REG_R15): Likewise.
	(struct _libc_fpstate): Likewise.
	(fpregset_t): Likewise.
	* sysdeps/unix/sysv/linux/hppa/sys/ucontext.h (NGREG): Likewise.
	(NFPREG): Likewise.
	(gregset_t): Likewise.
	(fpregset_t): Likewise.
	* sysdeps/unix/sysv/linux/m68k/sys/ucontext.h (R_D0): Likewise.
	(R_D1): Likewise.
	(R_D2): Likewise.
	(R_D3): Likewise.
	(R_D4): Likewise.
	(R_D5): Likewise.
	(R_D6): Likewise.
	(R_D7): Likewise.
	(R_A0): Likewise.
	(R_A1): Likewise.
	(R_A2): Likewise.
	(R_A3): Likewise.
	(R_A4): Likewise.
	(R_A5): Likewise.
	(R_A6): Likewise.
	(R_A7): Likewise.
	(R_SP): Likewise.
	(R_PC): Likewise.
	(R_PS): Likewise.
	(fpregset_t): Likewise.
	(MCONTEXT_VERSION): Likewise.
	* sysdeps/unix/sysv/linux/nios2/sys/ucontext.h (MCONTEXT_VERSION):
	Likewise.
	* sysdeps/unix/sysv/linux/sh/sys/ucontext.h (REG_R0): Likewise.
	(REG_R1): Likewise.
	(REG_R2): Likewise.
	(REG_R3): Likewise.
	(REG_R4): Likewise.
	(REG_R5): Likewise.
	(REG_R6): Likewise.
	(REG_R7): Likewise.
	(REG_R8): Likewise.
	(REG_R9): Likewise.
	(REG_R10): Likewise.
	(REG_R11): Likewise.
	(REG_R12): Likewise.
	(REG_R13): Likewise.
	(REG_R14): Likewise.
	(REG_R15): Likewise.
	* sysdeps/unix/sysv/linux/tile/sys/ucontext.h: Condition inclusion
	of <arch/abi.h> on [__USE_MISC].
	(greg_t): Condition on [__USE_MISC].
	(NGREG): Likewise.
	(gregset_t): Likewise.