Hi all,

This patch reimplements the vaba* arm_neon.h intrinsics using RTL builtins that expand to proper RTL patterns
rather than using inline asm.
The implementation is fairly straightforward by defining new builtins and using them in the header.

Bootstrapped and tested on aarch64-none-linux-gnu.

Pushing to trunk.
Thanks,
Kyrill

gcc/
	* config/aarch64/aarch64-simd-builtins.def (saba, uaba): Define builtins.
	* config/aarch64/arm_neon.h (vaba_s8): Implement using builtin.
	(vaba_s16): Likewise.
	(vaba_s32): Likewise.
	(vaba_u8): Likewise.
	(vaba_u16): Likewise.
	(vaba_u32): Likewise.
	(vabaq_s8): Likewise.
	(vabaq_s16): Likewise.
	(vabaq_s32): Likewise.
	(vabaq_u8): Likewise.
	(vabaq_u16): Likewise.
	(vabaq_u32): Likewise.