Change IsUTF8String more restrict. Do not allow surrogate char encode as UTF8

modules/rdf/src/utils.c

@@ -540,6 +540,10 @@ PRBool IsUTF8Text(const char* utf8, int32 len)
 	/* No enough trail bytes */
         if( (i + clen) > len) 
 	  return FALSE;
+	/* a single Surrogate should not show in 3 bytes UTF8, instead, the pair should be intepreted
+	   as one single UCS4 char and encoded UTF8 in 4 bytes */
+        if((0xED == utf8[i] ) && (0xA0 ==  (utf8[i+1] & 0xA0 ) )) 
+          return FALSE;
 	/* 0000 0000 - 0000 07FF : should encode in less bytes */
         if((0 ==  (utf8[i] & 0x0F )) && (0 ==  (utf8[i+1] & 0x20 ) )) 
           return FALSE;