Update README/TODO with new naming

ChangeLog

@@ -1654,7 +1654,7 @@
 	* arch/*/include/*/type.h: On some compilers, char defaults as unsigned.
 	  Explicitly add signed to integer types if signed is what is required.
 	* arch/*: For all architectures -- Global register state save structure
-	  (usually called current_regs) should be marked volatile; Added general
+	  (usually called g_current_regs) should be marked volatile; Added general
 	  capability to support nested interrupts (not fully realized for all
 	  architectures).
 	* sched/task_create.c: Add support for starting kernel-mode thread.

TODO

@@ -1679,7 +1679,7 @@ o ARM (arch/arm/)
   Title:       IMPROVED ARM INTERRUPT HANDLING
   Description: ARM interrupt handling performance could be improved in some
                ways. One easy way is to use a pointer to the context save
-               area in current_regs instead of using up_copystate so much.
+               area in g_current_regs instead of using up_copystate so much.
 
                This approach is already implemented for the ARM Cortex-M0,
                Cortex-M3, Cortex-M4, and Cortex-A5 families.  But still needs