Integrate perlio:

[ 14499]
Collect some stats during compile process.
Experiment with effect of bundling all EUC-JP, EUC-CN, EUC-KR
as one XS - inconclusive - marginal win?
Add some comments to encode.h

[ 14490]
Basics of a compiled Encode XS extension

p4raw-link: @14499 on //depot/perlio: b1e7e56f1e0264e9b11883bf65d50cc9648125ec
p4raw-link: @14490 on //depot/perlio: d811239cc9c7c7e9aec8cc641d1ae1aadd03c900

p4raw-id: //depot/perl@14500

diff --cc ext/Encode/compile
Simple merge