RISC-V: Minimal support of vector extensions

RISC-V: Minimal support of vector extensions

gcc/ChangeLog:

	* common/config/riscv/riscv-common.c (riscv_implied_info): Add
	vector extensions.
	(riscv_ext_version_table): Add version info for vector extensions.
	(riscv_ext_flag_table): Add option mask for vector extensions.
	* config/riscv/riscv-opts.h (MASK_VECTOR_EEW_32): New.
	(MASK_VECTOR_EEW_64): New.
	(MASK_VECTOR_EEW_FP_32): New.
	(MASK_VECTOR_EEW_FP_64): New.
	(MASK_ZVL32B): New.
	(MASK_ZVL64B): New.
	(MASK_ZVL128B): New.
	(MASK_ZVL256B): New.
	(MASK_ZVL512B): New.
	(MASK_ZVL1024B): New.
	(MASK_ZVL2048B): New.
	(MASK_ZVL4096B): New.
	(MASK_ZVL8192B): New.
	(MASK_ZVL16384B): New.
	(MASK_ZVL32768B): New.
	(MASK_ZVL65536B): New.
	(TARGET_ZVL32B): New.
	(TARGET_ZVL64B): New.
	(TARGET_ZVL128B): New.
	(TARGET_ZVL256B): New.
	(TARGET_ZVL512B): New.
	(TARGET_ZVL1024B): New.
	(TARGET_ZVL2048B): New.
	(TARGET_ZVL4096B): New.
	(TARGET_ZVL8192B): New.
	(TARGET_ZVL16384B): New.
	(TARGET_ZVL32768B): New.
	(TARGET_ZVL65536B): New.
	* config/riscv/riscv.opt (Mask(VECTOR)): New.
	(riscv_vector_eew_flags): New.
	(riscv_zvl_flags): New.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/predef-14.c: New.
	* gcc.target/riscv/predef-15.c: Ditto.
	* gcc.target/riscv/predef-16.c: Ditto.