Internal WT programs are using WT_UNUSED everywhere, test/bloom was the
last hold-out.   While in the area, noticed test/bloom doesn't need
signal or event handlers, fix function signatures, and there was an
extraneous newline written by the usage function.
Get rid of CONFIG.example, it's never correct, futz with the config
error output a little to make it more readable.
Allow replay of threaded runs.