qom: Add code block markup to all code blocks

Convert all example/codelisting markup to Sphinx code-block.

There are a few sections where backslashes at the end of lines
break code formatting.  A comment was added noting that this is
an issue.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <20200910221526.10041-8-ehabkost@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
1 file changed