[GCC, ARM] Enable armv8.5-a and add +sb and +predres for previous ARMv8-a in ARM

[GCC, ARM] Enable armv8.5-a and add +sb and +predres for previous ARMv8-a in ARM

This patch adds -march=armv8.5-a to the Arm backend.
Armv8.5-A also adds two new security features:
- Speculation Barrier instruction
- Execution and Data Prediction Restriction Instructions
These are made optional to all older Armv8-A versions. Thus we are adding two
new options "+sb" and "+predres" to all older Armv8-A. These are passed on to
the assembler and have no code generation effects and have already gone in the
trunk of binutils.

*** gcc/ChangeLog ***

2018-11-12  Sudakshina Das  <sudi.das@arm.com>

	* config/arm/arm-cpus.in (armv8_5, sb, predres): New features.
	(ARMv8_5a): New fgroup.
	(armv8.5-a): New arch.
	(armv8-a, armv8.1-a, armv8.2-a, armv8.3-a, armv8.4-a): New options
	sb and predres.
	* config/arm/arm-tables.opt: Regenerate.
	* config/arm/t-aprofile: Add matching rules for -march=armv8.5-a
	* config/arm/t-arm-elf (all_v8_archs): Add armv8.5-a.
	* config/arm/t-multilib (v8_5_a_simd_variants): New variable.
	Add matching rules for -march=armv8.5-a and extensions.
	* doc/invoke.texi (ARM options): Document -march=armv8.5-a.
	Add sb and predres to all armv8-a except armv8.5-a.

*** gcc/testsuite/ChangeLog ***

2018-11-12  Sudakshina Das  <sudi.das@arm.com>

	* gcc.target/arm/multilib.exp: Add some -march=armv8.5-a
	combination tests.

From-SVN: r266031