[1/3] cmd/tests: Use plain strings instead of char arrays for keywords

[Dan Kegel]

Frédéric Delanoy wrote:
-    static const char escaped_space[] = {'@','s','p','a','c','e','@','\0'};
+    static const char *escaped_space = "@space@";

I'm not sure it's worth the effort, since eventually we want
cmd to use unicode internally, at which point we'll have
to go back to using arrays.