Fix: Text array parsing disambiguates NULL and "NULL".

This solution is a little awkward, but it avoids breaking backwards
compatibility.

fixes #78

float4_array.go

@@ -319,7 +319,7 @@ func (dst *Float4Array) DecodeText(ci *ConnInfo, src []byte) error {
 		for i, s := range uta.Elements {
 			var elem Float4
 			var elemSrc []byte
-			if s != "NULL" {
+			if s != "NULL" || uta.Quoted[i] {
 				elemSrc = []byte(s)
 			}
 			err = elem.DecodeText(ci, elemSrc)