winedbg: Cleanup the process_io usage.

- made be_process_io references 'const'
- make use of it for dbg_read_memory and dbg_write_memory
diff --git a/programs/winedbg/be_i386.c b/programs/winedbg/be_i386.c
index f1ee7be..1dc001d 100644
--- a/programs/winedbg/be_i386.c
+++ b/programs/winedbg/be_i386.c
@@ -392,7 +392,7 @@
     return -1;
 }
 
-static unsigned be_i386_insert_Xpoint(HANDLE hProcess, struct be_process_io* pio, 
+static unsigned be_i386_insert_Xpoint(HANDLE hProcess, const struct be_process_io* pio, 
                                       CONTEXT* ctx, enum be_xpoint_type type, 
                                       void* addr, unsigned long* val, unsigned size)
 {
@@ -443,7 +443,7 @@
     return 1;
 }
 
-static unsigned be_i386_remove_Xpoint(HANDLE hProcess, struct be_process_io* pio,
+static unsigned be_i386_remove_Xpoint(HANDLE hProcess, const struct be_process_io* pio,
                                       CONTEXT* ctx, enum be_xpoint_type type, 
                                       void* addr, unsigned long val, unsigned size)
 {