Since the 16 domains are configured as the client domains in
mmu_setttbase(), a Permission fault is generated if the XN bit
(Execute-never) is set in the short-descriptor translation table
(for section and supersection). This leads to the booting failure
when enabling MMU for beagleboard bsp. Here is log:

----------------------------------------------------------------
SD/MMC found on device 0
reading uEnv.txt
117 bytes read in 3 ms (38.1 KiB/s)
Loaded environment from uEnv.txt
Importing environment from mmc ...
Running uenvcmd ...
reading rtthread.bin
162624 bytes read in 24 ms (6.5 MiB/s)
\## Starting application at 0x80200000 ...

----------------------------------------------------------------

This commit removes the XN bit configuration in the section of the
short-descriptor translation table. The OS can be booted successfully
with applying this commit.

1. Combine code for IAR and GCC in file mmu.c and cpuport.c
2. Remove remap code in start_xxx.S. User should config MMU to map vector table to visual address 0x0

1. [bsp][sam9260] Fix the bug that auto reset after boot 20s. Disable watchdog in rt_lovel_level_init function.
2. [bsp][sam9260] Modify SCONS scripts to support IAR tool chain.
3. [bsp][sam9260] Move link strips in to folder link_scripts.
4. [libcpu][arm926] Add copy right to source file and format code.

	..\..\libcpu\arm\cortex-m3\context_rvds.S(207):
	warning: A1581W: Added 2 bytes of padding at address 0xd6

vector_undef and vector_dabt

When RT-Thread is running stand alone, it forgot to enable the
distributor of GIC.

This piece of code will enable the interrupt early before switching to
the first thread. Although it is harmless, but not prefect.

Unit of "byte" is more intuitive than "long".

As the svc stack is the stack of threads, there is no need to allocate a
separate stack for the startup. Reuse the IRQ stack should be OK.

Tested on rm48 board.

for 2013-02-20 aozima commmit "port for gcc", but the commit is
not tested,and the kernel is breakdown in context_gcc.S, the file
is a copy from cortex-m3,but not port for cortex-m0, so i complete
this port for aozima, test it in stm32f0discovery board ,
and it works fine.

We could not handle any traps except IRQ/FIQ.

This fix a compile error in Clang.