Re: grep.el regexp

[Richard M. Stallman]

    With `-b' option GNU grep can output the byte offset of the beginning
    of the matching line counting from the beginning of the file, e.g.:

    emacs-2:1205:50533:inserts `xyzxyzxyzxyz' in the current buffer.

    This format resembles the output of column numbers, but it is not.
    It misleads grep.el into interpreting it as a column number.

    AFAIK, currently GNU grep doesn't support column number output.

It would be rather difficult to handle this byte-count
in Emacs, given the complexities of character set decoding.
So I think we should forget about that.

Meanwhile, if GNU grep doesn't support the column number output,
chances are no other does, and there's no reason for grep.el to
handle that output.  I would guess that it got copied into grep.el
from compile.el and that it was implemented for the sake of some
GCC front ends that do or might someday output this.

So in making this change in grep.el, those formats can be ignored.