new feature: .used pragma to suppress declared-but-not-used warning

doc/manual/pragmas.txt

@@ -503,6 +503,26 @@ identifier that can be used to enable or disable it:
 This is often better than disabling all warnings at once.
 
 
+used pragma
+-----------
+
+Nim produces a warning for symbols that are not exported and not used either.
+The ``used`` pragma can be attached to a symbol to suppress this warning. This
+is particularly useful when the symbol was generated by a macro:
+
+.. code-block:: nim
+  template implementArithOps(T) =
+    proc echoAdd(a, b: T) {.used.} =
+      echo a + b
+    proc echoSub(a, b: T) {.used.} =
+      echo a - b
+
+  # no warning produced for the unused 'echoSub'
+  implementArithOps(int)
+  echoAdd 3, 5
+
+
+
 experimental pragma
 -------------------