Add semantic patches to correctly check dns_name_copy(..., NULL) return code

Add semantic patches to correctly check dns_name_copy(..., NULL) return code

The dns_name_copy() function cannot fail gracefully when the last argument
(target) is NULL.  Add RUNTIME_CHECK()s around such calls.

The first semantic patch adds RUNTIME_CHECK() around any call that ignores the
return value and is very safe to apply.

The second semantic patch attempts to properly add RUNTIME_CHECK() to places
where the return value from `dns_name_copy()` is recorded into `result`
variable.  The result of this semantic patch needs to be reviewed by hand.

Both patches misses couple places where the code surrounding the
`dns_name_copy(..., NULL)` usage is more complicated and is better suited to be
fixed by a human being that understands the surrounding code.