reader-pscs: Set flag denoting change when reader is removed

When removed reader is detected for the first time,
set SC_READER_CARD_CHANGED denoting change. Remove
the flag, when the condition is hit again.

src/libopensc/reader-pcsc.c

@@ -407,7 +407,13 @@ static int refresh_attributes(sc_reader_t *reader)
 				|| rv == (LONG)SCARD_E_NO_READERS_AVAILABLE
 #endif
 				|| rv == (LONG)SCARD_E_SERVICE_STOPPED) {
- 			reader->flags &= ~(SC_READER_CARD_PRESENT);
+			/* Set flag when state changes */
+			if (reader->flags & SC_READER_REMOVED) {
+				reader->flags &= ~SC_READER_CARD_CHANGED;
+			} else {
+				reader->flags |= SC_READER_CARD_CHANGED;
+			}
+ 			reader->flags &= ~SC_READER_CARD_PRESENT;
 			reader->flags |= SC_READER_REMOVED;
 			priv->gpriv->removed_reader = reader;
  			SC_FUNC_RETURN(reader->ctx, SC_LOG_DEBUG_VERBOSE, SC_SUCCESS);