N new: number, as in e.g. N-PASSES or N-WORD-BITS
old: conventional prefix for temporary variables used to
implement evaluate-only-once semantics in macros
+ NLE non-local entry
+ NLX non-local exit (in compiler IR2)
SB storage base (in compiler IR2)
SC storage class (in compiler IR2)
TN temporary name (?) (in compiler IR2)