documentation bug for table-cell-horizontal-char

[harven]

There is a variable called table-cell-horizontal-char in the
emacs manual, version 22. This variable is said to contain
the character used as a horizontal delimiter for tables generated with
table.el.

There is in fact no table-cell-horizontal-char variable in table.el.
The variable is called instead table-cell-horizontal-chars and
contains  a string. Any character in this string is considered as a
horizontal delimiter when recognizing a table. The first character of
the string is used for output when drawing a new table.