Merge pull request #1400 from rbehrends/fix-stackscan

More robust implementation for finding the beginning of the stack.

lib/system.nim

@@ -2182,6 +2182,12 @@ when not defined(JS): #and not defined(NimrodVM):
         locals = addr(locals)
         setStackBottom(locals)
 
+    proc initStackBottomWith(locals: pointer) {.inline, compilerproc.} =
+      # We need to keep initStackBottom around for now to avoid
+      # bootstrapping problems.
+      when defined(setStackBottom):
+        setStackBottom(locals)
+
     var
       strDesc: TNimType