CTF: multi-CU and archive support

CTF: multi-CU and archive support

Now gdb is capable of debugging executable, which consists of multiple
compilation units (CUs) with the CTF debug info. An executable could
potentially have one or more archives, which, in CTF context, contain
conflicting types.

all changes were made in ctfread.c in which elfctf_build_psymtabs was
modified to handle archives, via the ctf archive iterator and its callback
build_ctf_archive_member and scan_partial_symbols was modified to scan
archives, which are treated as subfiles, to build the psymtabs.

Also changes were made to handle CTF's data object section and function
info section which now share the same format of their contents - an array
of type IDs. New functions ctf_psymtab_add_stt_entries, which is called by
ctf_psymtab_add_stt_obj and ctf_psymtab_add_stt_func, and add_stt_entries,
which is called by add_stt_obj and add_stt_func when setting up psymtabs
and full symtab, respectively.