Remove fpsetsticky(3) remains. It was removed with the recent libm update.

See FreeBSD's r143658 commit message for why it was removed.

This commit removes an orphaned extern declaration in x86_64's <ieeefp.h>,
syncs the fpgetround(3) manual page with FreeBSD and removes fpsetsticky's
MLINK.
bnx.4: Remove trailing whitespace.