Now that global -i is gone, pass -i through to the apropos(1)

Now that global -i is gone, pass -i through to the apropos(1)
expression parser, such that "apropos -i 'Nm~dump\>'"
finds kdump(1) and WCOREDUMP(2) and you don't need
to type the counter-intuitive "apropos -- -i 'Nm~dump\>'".