[Texmacs-dev] Documentation correction

[skhilji]

I noticed that there is a bug in the documentation of the <cwith> primitive in 
the Reference Guide of TeXmacs primitives.

It mentions <r, r, -1, 1>.  It should be <r, r, 1, -1>.  The one for the 
columns is also wrong.

I also noticed that the paragraph is a bit wordy.

I rewote this particular paragraph.  Here it is:

  Typical values for 
<with|mode|math|(<with|mode|text|<src-arg|top-row>>,<with|mode|text|<src-arg|bot-row>>,<with|mode|text|<src-arg|left-col>>,<with|mode|text|<src-arg|right-col>>)>
  are <with|mode|math|(r,r,<op|>1,<op|->1)> for ``row <with|mode|math|r>'',
  <with|mode|math|(<op|>1,<op|->1,c,c)> for ``column <with|mode|math|c>'',
  and <with|mode|math|(r,r,c,c)> for ``the cell at row <with|mode|math|r>,
  column <with|mode|math|c>''. When new cells are inserted, it makes a
  difference whether the rows are counted from the top or bottom, and the
  columns are counted from the left or right. If <with|mode|math|m> is the
  number of rows and <with|mode|math|n> the number of columns, then
  <with|mode|math|r> and <with|mode|math|r-m-1> represent the same
  row<emdash>the former is relative to the top border while the latter is
  relative the bottom border. Similarly, <with|mode|math|c> and
  <with|mode|math|c-n-1> represnt the same column.