qapi-schema: Improve section headings

qapi-schema: Improve section headings

The generated QEMU QMP reference is now structured as follows:

    1.1 Introduction
    1.2 Stability Considerations
    1.3 Common data types
    1.4 Socket data types
    1.5 VM run state
    1.6 Cryptography
    1.7 Block devices
    1.7.1 Block core (VM unrelated)
    1.7.2 QAPI block definitions (vm unrelated)
    1.8 Character devices
    1.9 Net devices
    1.10 Rocker switch device
    1.11 TPM (trusted platform module) devices
    1.12 Remote desktop
    1.12.1 Spice
    1.12.2 VNC
    1.13 Input
    1.14 Migration
    1.15 Transactions
    1.16 Tracing
    1.17 QMP introspection
    1.18 Miscellanea

Section "1.18 Miscellanea" is still too big: it documents 134 symbols.
Section "1.7.1 Block core (VM unrelated)" is also rather big: 128
symbols.  All the others are of reasonable size.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1503602048-12268-17-git-send-email-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>