Simplify AppleScript handling

[sellout]

This unifies the three separate copies of the AppleScript used to query the system’s mode.

Each of the three approaches has some changes

• ns-do-applescript uses AppleScript’s built-in boolean coercion to integer, since it doesn’t support AppleScript booleans;
• mac-do-applescript seems to return the command output as a string, so this avoids the extra conversion to an AppleScript string and returns the boolean directly; and
• osascript now uses process-lines instead of shell-command-to-string which avoids shell invocation, the need to handle any shell escaping in the arguments, and the need to trim the result (which is now a list of output lines).

[sellout]

I tested both the ns-do-applescript and osascript approaches, but I’m not sure where mac-do-applescript comes from. If you let me know, I will mention it in the doc/comments and test that approach as well.