Forward declaration of MemoryController.

My change to exec_context.hh probably affected these files to no longer have MemoryController forward declared through a long chain of includes.  MemoryController should be forward declared where it is used anyways.

dev/alpha_console.hh:
dev/uart.hh:
dev/uart8250.hh:
    Forward declaration of MemoryController.

--HG--
extra : convert_revision : afaac4014e0eb3b6d5d385cd4444b77511e03b51

dev/alpha_console.hh

@@ -43,6 +43,7 @@ class BaseCPU;
 class SimConsole;
 class AlphaSystem;
 class SimpleDisk;
+class MemoryController;
 
 /**
  * Memory mapped interface to the system console. This device

dev/uart.hh

@@ -37,6 +37,7 @@
 #include "dev/io_device.hh"
 
 class SimConsole;
+class MemoryController;
 class Platform;
 
 const int RX_INT = 0x1;

dev/uart8250.hh

@@ -53,6 +53,7 @@
 #define IIR_LINE  0x06 /* Rx Line Status (highest priority)*/
 
 class SimConsole;
+class MemoryController;
 class Platform;
 
 class Uart8250 : public Uart