Our documentation generator is a bit messy, to say the least. For
instance, the description to return values of a function is
searched within C comment. Currently, all lines that start with
'returns' or 'Returns' are viewed as return value description.
However, there are some valid uses where the 'returns' word is in
the middle of a sentence describing function behavior not the
return value. And there are no places where 'returns' is used to
describe return values.  For instance:
virDomainDetachDeviceFlags, virConnectNetworkEventRegisterAny and
virDomainGetDiskErrors. This leads to HTML documemtation being
generated incorrectly.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>