Aarch64: Detect FP regs in signal frame

Aarch64: Detect FP regs in signal frame

Both the VFP and SVE registers may be contained within the reserved space of
the sigcontext and can be found by seraching for MAGIC values. Detect these
and add the registers (including pseudos) to the trad frame cache.

gdb/
	* aarch64-linux-tdep.c (AARCH64_SIGCONTEXT_RESERVED_OFFSET): Add
	define.
	(AARCH64_EXTRA_MAGIC): Likewise.
	(AARCH64_FPSIMD_MAGIC): Likewise.
	(AARCH64_SVE_MAGIC): Likewise.
	(AARCH64_EXTRA_DATAP_OFFSET): Likewise.
	(AARCH64_FPSIMD_FPSR_OFFSET): Likewise.
	(AARCH64_FPSIMD_FPCR_OFFSET): Likewise.
	(AARCH64_FPSIMD_V0_OFFSET): Likewise.
	(AARCH64_FPSIMD_VREG_SIZE): Likewise.
	(AARCH64_SVE_CONTEXT_VL_OFFSET): Likewise.
	(AARCH64_SVE_CONTEXT_REGS_OFFSET): Likewise.
	(AARCH64_SVE_CONTEXT_P_REGS_OFFSET): Likewise.
	(AARCH64_SVE_CONTEXT_FFR_OFFSET): Likewise.
	(AARCH64_SVE_CONTEXT_SIZE): Likewise.
	(read_aarch64_ctx): Add function.
	(aarch64_linux_sigframe_init): Detect FP registers.