This changes struct frame_arg to be self-managing and then fixes the
various users.
Tested by the buildbot.
gdb/ChangeLog
2019-08-07 Tom Tromey <tromey@adacore.com>
* stack.c (print_frame_arg, read_frame_local, read_frame_arg)
(print_frame_args): Update.
* python/py-framefilter.c (py_print_single_arg, enumerate_args):
Update.
* mi/mi-cmd-stack.c (list_arg_or_local): Update.
* frame.h (struct frame_arg): Add initializers.
<error>: Now a unique_xmalloc_ptr.