[manual] Update introduction to the axis function

[Francesco Potorti`]

The axis function is no more limited to setting the axes limits, and the
current short introduction is misleading.  This patch adds just one line.

# HG changeset patch
# User Francesco Potortì <pot at gnu.org>
# Date 1222415920 -7200
# Node ID e51c66e1fbc0f390a03ab61b367485f631388b14
# Parent  255a2225678d9fc0c70addf0e5fa2499b88eae8f
Update introduction to the axis function.

diff -r 255a2225678d -r e51c66e1fbc0 doc/ChangeLog
--- a/doc/ChangeLog	Thu Sep 25 15:59:18 2008 +0200
+++ b/doc/ChangeLog	Fri Sep 26 09:58:40 2008 +0200
@@ -1,3 +1,8 @@
+2008-09-26  Francesco Potortì  <pot at gnu.org>
+
+	* interpreter/plot.txi (Two-Dimensional Plots): Update
+	introduction to the axis function.
+
 2008-09-25  Francesco Potortì  <pot at gnu.org>
 
 	* interpreter/plot.txi (Plot Annotations): Add cross reference to
diff -r 255a2225678d -r e51c66e1fbc0 doc/interpreter/plot.txi
--- a/doc/interpreter/plot.txi	Thu Sep 25 15:59:18 2008 +0200
+++ b/doc/interpreter/plot.txi	Fri Sep 26 09:58:40 2008 +0200
@@ -172,7 +172,8 @@
 @DOCSTRING(area)
 
 The axis function may be used to change the axis limits of an existing
-plot.
+plot and various other axis properties, such as the aspect ratio and the
+appearance of tic marks.
 
 @DOCSTRING(axis)