Add support for blob type in sqlite3... it's unusual in that it
is created into the table schema as a column of blob type, but is
not serialized or deserialized into or from JSON or sqlite.
Because the size of blobs is open-ended, accessing them in one
hit may not be possible, eg, exceed the size of available heap.
As binary, they would have to be base64-encoded in JSON
representation and that bloating may be excessive, with, eg,
a 500MB blob. So while they can be defined using lws_struct
schema, and coexist inside a column of a table managed by
lws_struct, they must be read and written separately.
Although the code is correct and the symbols should be defined, making some
prototypes conditional on cmake defines breaks their visibility when the
library is built.
They're conditional here to get around use of sqlite3 type in the prototypes
where we may not be including sqlite3 headers. Replace the conditional with
a grauitous typedef as a forward ref, since it's only referred to via
pointer types.
Continue with lws_struct, add sqlite support for one
level of lws_dll2_t lists of structs serialization and
deserialization, plus the matching api-test.
