New style size default behavior documentation

[jlacroix]

The default behavior of the style size has changed to the default symbol size.
We need to reflect that change in the documentation. See Bug 751 for more
information. In short, this will take the biggest Y value of the symbol
definition to set the default style size.

Is there anywhere else than the mapfile reference that needs to be changed?

[dmorissette]

updates needed in at least 2 places in the mapfile-reference.hml:

- Under "Class / SIZE [integer]"
  Change "Default size is 1" to: For vector (and ellipse) symbol types the
default size is based on the range of Y values in the POINTS defining the
symbol. For pixmaps, the default is the vertical size of the image. Default size
is 1 for TTF symbols. 

- Under "Symbology / POINTS [x y x y ...] END"
  Add a note explaining that if a class using this symbol doesn't contain an
explicit size, then the default symbol size will be based on the range of "y"
values in the point coordinates for a given. e.g. if the y coordinates of the
points in the symbol range from 0 to 5, then the default size for this symbol
will be assumed to be 5.

[jmckenna@…]

made changes as required.  fixed in dev version of doc.