implements the 'codegenDecl' pragma

doc/nimrodc.txt

@@ -399,6 +399,21 @@ interfacing with libraries written in Objective C:
 The compiler needs to be told to generate Objective C (command ``objc``) for 
 this to work. The conditional symbol ``objc`` is defined when the compiler
 emits Objective C code.
+
+
+CodegenDecl pragma
+------------------
+
+The `codegenDecl`:idx: pragma can be used to directly influence Nimrod's code
+generator. It receives a format string that determines how the variable or 
+proc is declared in the generated code:
+
+.. code-block:: nimrod
+  var
+    a {.codegenDecl: "$# progmem $#".}: int
+
+  proc myinterrupt() {.codegenDecl: "__interrupt $# $#$#".} =
+    echo "realistic interrupt handler"
 
 
 LineDir option