pipeline: clarify that applications should handle bus messages

The pipeline posts messages on the bus even if an application does not
handle the messages. This is expected behavior but may leak messages if
the messages are not handled.

Clarify the documentation.

Part-of: <gstreamer/gstreamer!680>
36 jobs for !680 with clarify-pipeline-bus-documentation in 29 minutes and 50 seconds (queued for 3 seconds)
detached
Status Job ID Name Coverage
  Build Docker
passed #6312955
alpine amd64 manifest builder docker

00:00:13

passed #6312954
android docker

00:00:30

passed #6312952
cerbero fedora amd64 docker

00:00:13

passed #6312950
fedora amd64 docker

00:00:13

passed #6312957
gst-indent amd64 docker

00:00:29

 
  Preparation
passed #6312962
check allow-edit

00:00:11

passed #6312960
gst indent

00:00:10

passed #6312959
manifest

00:00:27

 
  Build
passed #6312979
gstreamer
build cerbero cross-android universal

00:10:50

passed #6312987
gst-ios-13.2
build cerbero cross-ios universal

00:18:39

passed #6312981
gstreamer
build cerbero cross win32

00:08:31

passed #6312983
gstreamer
build cerbero cross win64

00:05:53

passed #6312977
gstreamer
build cerbero fedora x86_64

00:05:56

passed #6312985
gst-macos-10.15
build cerbero macos x86_64

00:09:37

passed #6312989
docker windows gstreamer-windows 1809
build cerbero msvc x86_64

00:12:09

passed #6312968
build clang fedora x86_64

00:09:55

manual #6312975
docker windows 1809 allowed to fail manual
build msys2
passed #6312963
build nodebug fedora x86_64

00:05:48

passed #6312965
build static fedora x86_64

00:07:56

passed #6312967
build static nodebug fedora x86_64

00:04:39

passed #6312970
docker windows 1809
build vs2017 amd64

00:09:56

passed #6312973
docker windows 1809
build vs2017 x86

00:10:09

 
  Test
passed #6312992
gstreamer
check fedora

00:10:02

passed #6312994
gstreamer
integration testsuites fedora 1/4

00:15:50

passed #6312996
gstreamer
integration testsuites fedora 2/4

00:19:23

passed #6312998
gstreamer
integration testsuites fedora 3/4

00:15:21

passed #6313000
gstreamer
integration testsuites fedora 4/4

00:28:43

passed #6313008
gstreamer
valgrind bad

00:05:10

passed #6313004
gstreamer
valgrind base

00:11:42

passed #6313002
gstreamer
valgrind core

00:09:24

passed #6313009
gstreamer
valgrind ges

00:07:26

passed #6313006
gstreamer
valgrind good

00:11:29

passed #6313007
gstreamer
valgrind ugly

00:03:36

 
  Integrate
passed #6313010
cross-android universal examples

00:06:41

passed #6313012
gst-ios-13.2
cross-ios universal examples

00:03:14

passed #6313011
documentation

00:11:43