Don't segv on cie.initial_instructions[] overflow.

Don't segv on cie.initial_instructions[] overflow.

Don't attempt to merge CIEs with a larger number of insns than will
fit in the buffer.

	* elf-eh-frame.c (cie_eq): Return false when initial_insn_length
	is too large.
	(cie_compute_hash): Don't exceed bounds of initial_instructions.
	(_bfd_elf_parse_eh_frame): Always set initial_insn_length, and
	save as much of insns to initial_instructions[] as will fit.