improve multiple results support
The specification talks exactly about -1:
> Returns: the current result as an update count;
> -1 if the current result is a ResultSet object or there are no more results
Other negative numbers can theoretically mean something different than „no more results“
e.g. unknown number of updates (?).
# This code depends on make tool being used
DEPFILES=$(wildcard $(addsuffix .d, ${OBJECTFILES} ${TESTOBJECTFILES}))
ifneq (${DEPFILES},)
include ${DEPFILES}
endif