implemented 'injectStmt'; more debug support

doc/manual.txt

@@ -5053,6 +5053,18 @@ Note that this pragma is somewhat of a misnomer: Other backends will provide
 the same feature under the same name.
 
 
+Extern pragma
+-------------
+Like ``exportc`` or ``importc`` the `extern`:idx: pragma affects name
+mangling. The string literal passed to ``extern`` can be a format string:
+
+.. code-block:: Nimrod
+  proc p(s: string) {.extern: "prefix$1".} =
+    echo s
+
+In the example the external name of ``p`` is set to ``prefixp``.
+
+
 Bycopy pragma
 -------------
 

doc/nimrodc.txt

@@ -468,6 +468,19 @@ proc is declared in the generated code:
 
   proc myinterrupt() {.codegenDecl: "__interrupt $# $#$#".} =
     echo "realistic interrupt handler"
+
+
+InjectStmt pragma
+-----------------
+
+The `injectStmt`:idx: pragma can be used to inject a statement before every
+other statement in the current module. It is only supposed to be used for
+debugging:
+
+.. code-block:: nimrod
+  {.injectStmt: gcInvariants().}
+  
+  # ... complex code here that produces crashes ...
 
 
 LineDir option