  \/ F I - I M M E D I A T E _ M A C R O \/

Define a new macro and obey it straight away.

Immediate macros can be used to avoid the need to put real control characters in
U-USE files and / or to invoke arbitrary macros from the command source.
 Immediate macros have a small stack, (currently 16) and use otherwise
inaccessible macros N101 (macro 65) onwards. Like any macro, an immediate macro
can loop back to its own start by ^N^@, but immediate macros cannot reference
one another.
 Parameter
 <macro text> The unquoted definition (as if defined using N-NEWMACRO with a
              macro id of 3 or more octal digits) ("h n" gives more details).
 Q's -i option generates an FI command.
