[WMS-Client-Howto] Do not use EPSG:42304 in examples

[dmorissette]

A user pointed on the list that an example in the WMS Client HOWTO was using
EPSG:42304 but this projection doesn't exist in their default EPSG file:
http://mapserver.gis.umn.edu/docs/howto/wms_client/#adding-a-wms-layer

I think he's right that the examples should not rely on optional projection
codes, the fix could be as simple as changing EPSG:42304 for EPSG:4326 in this
example and in the explanations that follow.

While we're at it, I noticed that the URLs to download the custom epsg files
still point to www2.dmsolutions.ca at
http://mapserver.gis.umn.edu/docs/howto/wms_client/#install-optional-proj4-epsg-codes
The URLs should be updated to point to the files on the maptools.org/dl/ site.

I guess I could have made those changes myself but I thought I'd leave that up
to Jeff since he's the owner of that doc.

[tomkralidis]

I've made these changes to ​http://mapserver.gis.umn.edu/docs/howto/wms_client/howto_view as per above. Closing.