Patch for EMBLOD boot loader for AVR32 platform

[Martin Guy]

Hi
  emBLOD is Marcus Jansson's second-stage boot loader for AVR32UC3A
parts as used in the EVK1100 and Mizar32 boards, designed to allow
firmware images larger than the on-chip flash memory by loading the
eLua binary from SD card into SDRAM and executing it there.

The source for the emBLOD loader is here https://github.com/cmp1084/emBLOD

The attached patch is for eLua svn r975 (current) for eLua.  When
compilation option  bootloader=emblod is given to scons, a special
version is compiled that
- locates the program at the start of SDRAM
- doesn't initialize the system clocks and SDRAM controller, as these
are already set up by emBLOD.

If the bootloader= option is not given, eLua is compiled exactly as before.

The changes I've made to Marcus' originally posted patches are to put
DATA and BSS in internal static RAM, the same as before, since in the
best case (memcpy) the SDRAM is three times slower than access to
static RAM
http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=80657

This also has an impact on code speed: the interpreter runs 9 times
slower in external SDRAM than it does in internal flash.

Tested and working on Mizar32

     M

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