Rename TARGET_OBJECT_AIX_LIBRARIES to TARGET_OBJECT_LIBRARIES_AIX

More consistent with the name of other similar object names.

gdb/ChangeLog:

	* target.h (enum target_object) [TARGET_OBJECT_LIBRARIES_AIX]:
	Renames TARGET_OBJECT_AIX_LIBRARIES.
	* rs6000-nat.c: Replace TARGET_OBJECT_AIX_LIBRARIES with
	TARGET_OBJECT_LIBRARIES_AIX throughout.
	* solib-aix.c: Likwise.
AIX: Change XML to use library-list-aix instead of library-list.

This is more consistent with what we do with other similar XML lists,
and avoids a potential confusion with the library-list XML list.

gdb/ChangeLog:

        * features/library-list-aix.dtd: Replace library-list by
        library-list-aix.
        * rs6000-nat.c: Replace library-list by library-list-aix
        throughout.
        * solib-aix.c: Likewise.