pgtype DecodeText and DecodeBinary do not copy

They now take ownership of the src argument.

Needed to change Scan to make a copy of []byte arguments as lib/pq apparently
gives Scan a shared memory buffer.

pgtype/float4_array.go

@@ -308,7 +308,9 @@ func (dst *Float4Array) Scan(src interface{}) error {
 	case string:
 		return dst.DecodeText(nil, []byte(src))
 	case []byte:
-		return dst.DecodeText(nil, src)
+		srcCopy := make([]byte, len(src))
+		copy(srcCopy, src)
+		return dst.DecodeText(nil, srcCopy)
 	}
 
 	return fmt.Errorf("cannot scan %T", src)