A table with OIDs that was the first in the dump output would not get
dumped with OIDs enabled.  Fix that.

The reason was that the currWithOids flag was declared to be bool but
actually also takes a -1 value for "don't know yet".  But under
stdbool.h semantics, that is coerced to true, so the required SET
default_with_oids command is not output again.  Change the variable
type to char to fix that.
Reported-by: Derek Nelson <derek@pipelinedb.com>