missing manpage for bridge.conf

This bug has been copied automatically from: https://bugs.launchpad.net/qemu/+bug/1424237

There's currently no (easy) way to figure out the form of content of
`/etc/qemu/bridge.conf`. Some howtos (e.g.
https://wiki.archlinux.org/index.php/QEMU#Bridged_networking_using_qemu-
bridge-helper) mention `bridge.conf.sample` which is not available
according to `apt-file` and the official wiki at wiki.qemu.org doesn't
mention the file at all, it seems necessary, though, because specification
of `-net nic -net bridge,br=bridge0` fails with `failed to get mtu of
bridge `bridge0': No such device` (can't be investigated further because
setup is completely unclear).

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: qemu 2.1+dfsg-4ubuntu6.4
Uname: Linux 3.19.0-031900-generic x86_64
ApportVersion: 2.14.7-0ubuntu8.2
Architecture: amd64
CurrentDesktop: Unity
Date: Sat Feb 21 19:39:07 2015
EcryptfsInUse: Yes
InstallationDate: Installed on 2015-01-26 (25 days ago)
InstallationMedia: Ubuntu 14.10 "Utopic Unicorn" - Release amd64
(20141022.1)
KvmCmdLine:
 COMMAND         STAT  EUID  RUID   PID  PPID %CPU COMMAND
 kvm-irqfd-clean S<       0     0  1026     2  0.0 [kvm-irqfd-clean]
 qemu-system-x86 Sl+      0     0 25905 25904 11.9 qemu-system-x86_64
-boot c -hda ubuntu.img -m 2048 -smp 16 -enable-kvm -vnc :0,abc -k de
-drive file=/dev/sda14,if=ide -net nic -net bridge,br=bridge0
 kvm-pit/25905   S        0     0 25948     2  0.0 [kvm-pit/25905]
MachineType: LENOVO 20221
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.19.0-031900-generic
root=UUID=ac20c93a-0ec5-445a-98cd-941f0fbc0e50 ro rootflags=subvol=@
SourcePackage: qemu
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 07/12/2013
dmi.bios.vendor: LENOVO
dmi.bios.version: 71CN51WW(V1.21)
dmi.board.asset.tag: No Asset Tag
dmi.board.name: INVALID
dmi.board.vendor: LENOVO
dmi.board.version: 31900003WIN8 STD MLT
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Lenovo IdeaPad Z500 Touch
dmi.modalias:
dmi:bvnLENOVO:bvr71CN51WW(V1.21):bd07/12/2013:svnLENOVO:pn20221:pvrLenovoIdeaPadZ500Touch:rvnLENOVO:rnINVALID:rvr31900003WIN8STDMLT:cvnLENOVO:ct10:cvrLenovoIdeaPadZ500Touch:
dmi.product.name: 20221
dmi.product.version: Lenovo IdeaPad Z500 Touch
dmi.sys.vendor: LENOVO