Make uifc.input.CTX and uifc.showbuf.CTX constructors match assumptions/docs

This one has caught me up before, for the CTX constructors didn't actually
accept any initial property values (as arguments).

mlong even documented it this way at
https://wiki.synchro.net/ref:uifc#javascript_interface

And construted his input.CTXs this way (using all 0 values, which were
ignored) in his xtrnmenucfg.js