Initial SPI implementation.

Squashed commit of the following:

commit b41eb846ca60559cff242d0c550699eb8f309909
Author: Perry Hung <iperry@alum.mit.edu>
Date:   Sat Apr 24 04:09:16 2010 -0400

    Turn the other peripherals back on. Not extensively tested for
    interactions between peripherals.

commit bf4fc3bf6bc02342ae508b52fb4515d361d626f6
Author: Perry Hung <iperry@alum.mit.edu>
Date:   Sat Apr 24 03:16:35 2010 -0400

    Upper level libmaple interface

    Added a C++ HardwareSPI class to access the SPI interface. See
    HardwareSPI.cpp and HardwareSPI.h for documentation.

commit 17e0e5edde60e9bf2aa4d52173ad7d47d6d6da75
Author: Perry Hung <iperry@alum.mit.edu>
Date:   Thu Apr 22 02:36:01 2010 -0400

    Initial SPI Polling implementation.

    Initial commit of a polling-based SPI driver. The driver is limited to
    synchronous, blocking sends and a 8-bit data frame format. Tested on
    SPI1 and SPI2.

    Other peripherals are temporarily disabled, and the rx function
    is untested until I find a good peripheral to test everything on.

1 files changed, 2 insertions, 0 deletions

diff --git a/libmaple/libmaple_types.h b/libmaple/libmaple_types.h
index ca98f6f..d49f95a 100644
--- a/libmaple/libmaple_types.h
+++ b/libmaple/libmaple_types.h
@@ -43,5 +43,7 @@ typedef long long int64;
 
 typedef void (*voidFuncPtr)(void);
 
+#define __io volatile
+
 #endif