Add pystack definition to Misc/gdbinit with some explanation of its behavior
and add flag comments to ceval.c and main.c alerting people to the coupling
between pystack and the layout of those files.
diff --git a/Modules/main.c b/Modules/main.c
index 68a82c7..fc5773c 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -452,6 +452,9 @@
 	return sts;
 }
 
+/* this is gonna seem *real weird*, but if you put some other code between
+   Py_Main() and Py_GetArgcArgv() you will need to adjust the test in the
+   while statement in Misc/gdbinit:ppystack */
 
 /* Make the *original* argc/argv available to other modules.
    This is rare, but it is needed by the secureware extension. */