qemu-system-i386 no longer boots NetBSD
Description of problem:
Since qemu commit e3a79e0e87831602e41819591a8e6dcc70a2a231, NetBSD
no longer boots under qemu-system-i386.
Steps to reproduce:
1. `wget http://ftp.netbsd.org/pub/NetBSD/NetBSD-9.2/i386/installation/cdrom/boot-com.iso`
2. `qemu-system-i386 -nographic -cdrom boot-com.iso`

Expected behavior: the system boots and prompts you for a terminal type with

    Terminal type (just hit ENTER for 'vt220'):

Observed incorrect behavior: the guest kernel either hangs during boot at

    Loading /stand/i386/9.2/modules/cd9660/cd9660.kmod  
    WARNING: 1 module failed to load

or panics during boot with

    kernel: supervisor trap page fault, code=0
    Stopped in pid 0.1 (system) at  netbsd:idt_vec_reserve+0xa:     cmpb    $0,netbs
    d:idt_allocmap(%ebx)
    db{0}>
Additional information:
This regression is a critical issue to the NetBSD project as its automated
testing infrastructure is heavily dependent on qemu-system-i386.