[PATCH 21.4] Add line-beginning-position, line-end-position

21.4 (already in 21.5) This patch adds line-beginning-position and line-end-position to the 21.4 series. We've seen these being erratically used here and there in packages a few times and lisp things out there outside of the packages tree uses these functions pretty often, I guess they're thought of as ubiquitous by many. The latest problem due to lack of these functions I'm aware of was reported as https://bugzilla.redhat.com/192481 : the current haskell-mode's indentation is broken on 21.4. Jerry, in case you're around, it could be a good idea to fix haskell-*indent.el to not use line-(beginning|end)-position in the meantime.