sockets.recv optimizations; stdlib now supports taint mode

doc/manual.txt

@@ -3402,3 +3402,25 @@ The interaction between threads and exceptions is simple: A *handled* exception
 in one thread cannot affect any other thread. However, an *unhandled* 
 exception in one thread terminates the whole *process*!
 
+Taint mode
+==========
+
+The Nimrod compiler and standard library support a `taint mode`:idx:. 
+Input strings are declared with the `TaintedString`:idx: string type declared
+in the ``system`` module.
+
+If the taint mode is turned on (via the ``--taintMode:on`` command line 
+option) it is a distinct string type which helps to detect input
+validation errors:
+
+.. code-block:: nimrod
+  echo "your name: "
+  var name: TaintedString = stdin.readline
+  # it is safe here to output the name without any input validation, so
+  # we simply convert `name` to string to make the compiler happy: 
+  echo "hi, ", name.string
+
+If the taint mode is turned off, ``TaintedString`` is simply an alias for
+``string``.
+
+