[ 16285]
Attempt at sanity in PerlIO/makedef.pl world:
1. Add comments to what each clump of symbols is for
2. Explicitly export layer syms like I thought they were
3. Remove bulk of (now redundant) PerlIO stuff from the <DATA>
section.
4. Re-sort perlio.sym
p4raw-link: @16285 on //depot/perlio:
d892637e7ede1a308d13f1482c6352a1b7bb28e4
p4raw-id: //depot/perl@16287