el/dot-emacs.el: Add machinery for not renaming buffers along with files.

el/dot-emacs.el: Add machinery for not renaming buffers along with files.

For example: if `backup-by-copying' is nil (which it is for me), then
`backup-buffer' will rename the file to its backup name -- and then
we'll be left visiting the backup file, which is obviously hopeless.

Add a variable `mdw-inhibit-rename-buffer' which instructs the
`rename-file' advice not to rename the buffer as well, and a new macro
`mdw-advise-to-inhibit-rename-buffer' to advise various functions to set
this variable while they're operating.