RFR: 8019551: Make BaseStream public

[Henry Jen]

Hi,

Please review webrev at

http://cr.openjdk.java.net/~henryjen/ccc/8019551/0/webrev/

This webrev makes BaseStream interface public and has AbstractPipeline
implements BaseStream.

The discussion on make this public can be found at

http://mail.openjdk.java.net/pipermail/lambda-libs-spec-experts/2013-July/002113.html

Cheers,
Henry