We are generating some Avro schemas where some type names had a leading
dot, to indicate the null namespace. For example:
```
{
"type": "record",
"name": ".envelope",
"fields": [ ... ]
}
```
This seems fine according to my reading of the 1.9.2 spec, but
explicitly disallowed by this language in the 1.10.1 spec: "The null
namespace may not be used in a dot-separated sequence of names."
So, my interpretation of 1.10.1 is that we have to write something like:
```
{
"type": "record",
"name": "envelope",
"namespace": "",
"fields": [ ... ]
}
```
However, this is explicitly _disallowed_ by the definition of Parsing
Canonical Form, which requires `namespace` attributes to be stripped:
"[FULLNAMES] Replace short names with fullnames, using applicable
namespaces to do so. Then eliminate namespace attributes, which are now
redundant."
Thus it seems now impossible to convert schemas into Parsing Canonical Form.
How can we get around this apparent inconsistency?
