increasing performance of nios 2

The JTAG debug doesn't affect the execution time of normal code.

For best performance:

- Make sure you compile everything (including the BSP/C library) with -O2 or -O3.

- Don't use floating point.

- Don't use printf.

- Try to use as little of the C libarary as possible.

- Fit all your code and data into tightly coupled memory.

- Don't use Altera's alt_main() code unless you really need the stdio setup and teardown (forces malloc() and friends into your image).

- Use the 'small data' segment (%gp relative addressing) for as much data as possible.

- Write C very carefully to give the compiler the best chance of optimising the code.