Fix lambda macro having parameters in wrong namespace

[stag-enterprises]

When using the ^() macro, it sometimes declares the argument variables into the rutils.readtable package, instead of the current package. For example:

(macroexpand '^(+ % %%))
; produces
#'(LAMBDA (&OPTIONAL RUTILS.READTABLE:% RUTILS.READTABLE:%%)
  (DECLARE (IGNORABLE RUTILS.READTABLE:%) (IGNORABLE RUTILS.READTABLE:%%))
  (+ % %%))

As you can see, the % and %% variables used in + are not the same as the ones defined as a parameter, so this will error. The solution is to use INTERN, so that the % and %% variables are declared in the correct package (the current one in the evaluation of the macro).