libctf: introduce ctf_func_type_{info,args}, ctf_type_aname_raw

libctf: introduce ctf_func_type_{info,args}, ctf_type_aname_raw

The first two of these allow you to get function type info and args out
of the types section give a type ID: astonishingly, this was missing
from libctf before now: so even though types of kind CTF_K_FUNCTION were
supported, you couldn't find out anything about them.  (The existing
ctf_func_info and ctf_func_args only allow you to get info about
functions in the function section, i.e. given symbol table indexes, not
type IDs.)

The second of these allows you to get the raw undecorated name out of
the CTF section (strdupped for safety) without traversing subtypes to
build a full C identifier out of it.  It's useful for things that are
already tracking the type kind etc and just need an unadorned name.

include/
	* ctf-api.h (ECTF_NOTFUNC): Fix description.
	(ctf_func_type_info): New.
	(ctf_func_type_args): Likewise.
libctf/
	* ctf-types.c (ctf_type_aname_raw): New.
	(ctf_func_type_info): Likewise.
	(ctf_func_type_args): Likewise.
	* ctf-error.c (_ctf_errlist): Fix description.