recent changes to svn

I just made some changes to svn that I want to mention. Sometimes, usetex's
external dependencies could fail silently. Andrew suggested that the
subprocess module included in python-2.4 could be used to catch the exit
status and therefore report such problems. I added this module to mpl; tests
on both linux systems with python-2.3 and python-2.4 were successful. Now if
you pass give latex bad syntax, an exception is raised and you will see the
report from latex.

I also added a papertype kwarg for postscript. You can do something like

savefig('test.eps', papertype='letter')

or if you want the pagesize to scale automatically:

savefig('test.eps', papertype='auto')

Adding the papertype kwarg actually required a small change to every backend.
I tested my work with backend_driver, and no problems turned up. Please let
me know if you experience problems.

Finally, I got landscape orientation working properly with the usetex option.
This wasnt an easy task, and I'll leave out the gory details, but I will say
I've been pulling my hair out all weekend and my eyes are crossed.