Remove ARM __ASSUME_SIGFRAME_V2.

This patch removes ARM __ASSUME_SIGFRAME_V2 now that the
2.6.18-and-later signal frame layout can be assumed, renaming the
affected functions accordingly now only one version of them is needed
in glibc.  (sigrestorer.S did not in fact include <kernel-features.h>
and it appears that, unlike other such cases, it didn't get the header
indirectly, so the v1 functions would have been compiled in even when
sigaction.c didn't reference them.)

(alpha and hppa also have architecture-specific __ASSUME_* macros that
should now be removed: __ASSUME_FDATASYNC and __ASSUME_LWS_CAS
respectively.  I don't have any plans to do anything on that myself.)

Tested on ARM.

	* sysdeps/unix/sysv/linux/arm/kernel-features.h
	(__ASSUME_SIGFRAME_V2): Remove macro.
	* sysdeps/unix/sysv/linux/arm/sigrestorer.S: Update comment.
	[!__ASSUME_SIGFRAME_V2]: Remove conditional code.
	(__default_sa_restorer_v2): Rename to __default_sa_restorer.
	(__default_rt_sa_restorer_v2): Rename to __default_rt_sa_restorer.
	* sysdeps/unix/sysv/linux/arm/sigaction.c (__default_sa_restorer):
	Declare as function.  Remove conditional macro definitions.
	(__default_rt_sa_restorer): Likewise.
	(__default_sa_restorer_v1): Remove declaration.
	(__default_sa_restorer_v2): Likewise.
	(__default_rt_sa_restorer_v1): Likewise.
	(__default_rt_sa_restorer_v2): Likewise.
	* sysdeps/unix/sysv/linux/arm/Versions (GLIBC_PRIVATE): Remove
	__default_sa_restorer_v1, __default_rt_sa_restorer_v1,
	__default_sa_restorer_v2 and __default_rt_sa_restorer_v2.