(Buffers): Add xrefs to Mode Line and Lisp Interaction.

(Buffers): Add xrefs to Mode Line and Lisp Interaction.
(Select Buffer): Mention use of minibuffer history.  Describe default
value of default-major-mode.  Mention that C-x 4 b selects the other
window.
(List Buffers): Document CRM indicators in the order they appear.
(Kill Buffer): Document new command kill-matching buffers.
(Several Buffers): Move explanation of the relationship between buffer
list and buffer menu to the top.
(Indirect Buffers): Document new variable clone-indirect-buffer-hook.