Config for NS build

[takaxp]

I have checked the default configuration in NS build and EMP build.
And I found we can only use fit-frame-to-buffer to show input keys.

However, in that case, we have to specify keycaster-use-child-frame as t for NS build.
When I use nil for NS build, then an error related to keycaster-pre-commend is reported.

|                           | NS  | NS  | EMP | EMP |
|---------------------------+-----+-----+-----+-----|
| fit-frame-to-buffer       | YES | YES | YES | YES |
| keycaster-use-child-frame | nil | t   | nil | t   |
|---------------------------+-----+-----+-----+-----|
|                           | NG  | OK! | OK! | OK! |

NS build: Emacs 27.0.60, 26.3.50
EMP build: Emacs 26.3

[chuntaro]

Thanks!