Bug 10077

When wildcard probing function returns, invariably one hits a problem:

[ananth@... ~]$ stap -ve 'probe kernel.function("*@fs/exec.c").return {
printf("%s\n", $return) }'
Pass 1: parsed user script and 51 library script(s) in 520usr/40sys/925real ms.
semantic error: function free_bprm(fs/exec.c) has no return value: identifier
'$return' at <input>:1:62
        source: probe kernel.function("*@fs/exec.c").return { printf("%s\n",
$return) }
                                                                             ^
Pass 2: analyzed script: 29 probe(s), 19 function(s), 0 embed(s), 0 global(s) in
370usr/760sys/1399real ms.
Pass 2: analysis failed.  Try again with another '--vp 01' option.

Would it be possible to emit a warning or a string "no $return in this context"
instead of aborting as above?