libbacktrace: update xcoff.c for base_address changes

	* xcoff.c (struct xcoff_fileline_data): Change base_address field
	to struct libbacktrace_base_address.
	(xcoff_initialize_syminfo): Change base_address to struct
	libbacktrace_base_address.  Use libbacktrace_add_base.
	(xcoff_initialize_fileline): Likewise.
	(xcoff_lookup_pc): Use libbacktrace_add_base.
	(xcoff_add): Change base_address to struct
	libbacktrace_base_address.
	(xcoff_armem_add, xcoff_add_shared_libs): Likewise.
	(backtrace_initialize): Likewise.
	* Makefile.am (xcoff.lo): Remove unused target.
	(xcoff_32.lo, xcoff_64.lo): New targets.
	* Makefile.in: Regenerate.