more minor items about graphics handles

[Michael D Godfrey]

I just noticed the get(0,"default<xxxxx>") syntax.
Is this why "default" is special?  So far,
the only example that I know of the above syntax is:
get(0,"defaultfigure__backend__").  Other strings for
<xxxxxx> produce, for example for <xxxxx> set to
screensize, you get:
error: get: invalid default property `screensize'

I will try to figure this out, but a quick pointer would help.

Michael