process_debug_info

This patch constrains process_debug_info to stay within the data
specified by the CU length rather than allowing access up to the end
of the section.

	* dwarf.c (process_debug_info): Always do the first CU length
	scan for sanity checks.  Remove initial_length_size var and
	instead calculate end_cu.  Use end_cu to limit data reads.
	Delete now dead code checking length.