Export redesign

this is an atempt to make the export of functions typesafe.
I replaced the jumptable void ** by a struct (jt_funcs) with function pointers.
The EXPORT_FUNC macro now has 3 fixed parameters and one
variadic parameter
The first is the name of the exported function,
the rest of the parameters are used to format a functionpointer
in the jumptable,

the EXPORT_FUNC macros are expanded three times,
1. to declare the members of the struct
2. to initialize the structmember pointers
3. to call the functions in stubs.c

Signed-off-by: Martin Dorwig <dorwig@tetronik.com>
Acked-by: Simon Glass <sjg@chromium.org>

Signed-off-by: Simon Glass <sjg@chromium.org>
(resending to the list since my tweaks are not quite trivial)
diff --git a/include/asm-generic/global_data.h b/include/asm-generic/global_data.h
index 3d14d5f1..6747619 100644
--- a/include/asm-generic/global_data.h
+++ b/include/asm-generic/global_data.h
@@ -73,7 +73,7 @@
 	const void *fdt_blob;	/* Our device tree, NULL if none */
 	void *new_fdt;		/* Relocated FDT */
 	unsigned long fdt_size;	/* Space reserved for relocated FDT */
-	void **jt;		/* jump table */
+	struct jt_funcs *jt;		/* jump table */
 	char env_buf[32];	/* buffer for getenv() before reloc. */
 #ifdef CONFIG_TRACE
 	void		*trace_buff;	/* The trace buffer */