If a record type named in a device() entry does not exist when
the device is seen, the DBD parser will now print a warning
and create an empty record type with that name to hold the
device entry information.
This will allow support modules to be built into libraries that
include their own registerRecordDeviceDriver code, which was
apparently possible with 3.14 although not officially supported.
To avoid the warning message, the DBD file can declare each
record type before the device statement that uses it.
A record type declaration looks like this:
recordtype(ao) {}
device(ao, ....)
An IOC will accept and ignore a record type declaration, but it
must have loaded the full record type definition first.
Source DBD files can include Pod blocks, as long as the dbdExpand.pl
script doesn't try and include it in expanded DBD output files.
This makes it easier to write the Pod, and perldoc can parse most
of the result for checking (it complains about the =field directives
though, which dbdToHtml.pl handles itself).
Record types cannot be duplicated however.
DBD sub-objects now have a ->what method for their description.
This also adds a method to look up a breaktable by name.
