text_reader: support quick-xml without encoding_rs dependency

src/encoding_type.rs

@@ -68,6 +68,12 @@ impl EncodingType {
     Ok(val)
   }
 
+  pub fn from_label(label: &[u8]) -> Result<Self, KbinError> {
+    Encoding::for_label(label)
+      .ok_or(KbinErrorKind::UnknownEncoding.into())
+      .and_then(Self::from_encoding)
+  }
+
   pub fn to_byte(&self) -> u8 {
     match *self {
       EncodingType::None       => 0x00, // 0x00 >> 5 = 0

src/text_reader.rs

@@ -216,8 +216,10 @@ impl<'a> TextXmlReader<'a> {
             parent_collection.children_mut().push_back(collection);
           }
         },
-        Ok(Event::Decl(_)) => {
-          self.encoding = EncodingType::from_encoding(self.xml_reader.encoding())?;
+        Ok(Event::Decl(e)) => {
+          if let Some(encoding) = e.encoding() {
+            self.encoding = EncodingType::from_label(&encoding?)?;
+          }
         },
         Ok(Event::Eof) => break,
         Ok(_) => {},