pgtype.Encode(Binary|Text) do not write length

To aid in composability, these methods no longer write their own length. This
is especially useful for text formatted arrays and may be useful for future
database/sql compatibility. It also makes the code a little simpler as the
types no longer have to compute their own size.

Along with this, these methods cannot encode NULL. They now return a boolean
if they are NULL. This also benefits text array encoding as numeric arrays
require NULL to be exactly `NULL` while string arrays require NULL to be
`"NULL"`.

cidrarray.go

@@ -22,10 +22,10 @@ func (dst *CidrArray) DecodeBinary(src []byte) error {
 	return (*InetArray)(dst).DecodeBinary(src)
 }
 
-func (src *CidrArray) EncodeText(w io.Writer) error {
+func (src *CidrArray) EncodeText(w io.Writer) (bool, error) {
 	return (*InetArray)(src).EncodeText(w)
 }
 
-func (src *CidrArray) EncodeBinary(w io.Writer) error {
+func (src *CidrArray) EncodeBinary(w io.Writer) (bool, error) {
 	return (*InetArray)(src).encodeBinary(w, CidrOID)
 }