Fixed SYS_ARCH_PROTECT macros when NO_SYS is not defined.

Added documentation for lightweight protection.

Fixed debug statement in ip.c.

Removed tabs in files I changed.

doc/sys_arch.txt

@@ -121,3 +121,26 @@ to be implemented as well:
   "thread()". The "arg" argument will be passed as an argument to the
   thread() function. The id of the new thread is returned.
 
+- sys_prot_t sys_arch_protect(void)
+
+This optional function does a "fast" critical region protection and returns
+the previous protection level. This function is only called during very short
+critical regions. An embedded system which supports ISR-based drivers might
+want to implement this function by disabling interrupts. Task-based systems
+might want to implement this by using a mutex or disabling tasking. This
+function should support recursive calls from the same task or interrupt. In
+other words, sys_arch_protect() could be called while already protected. In
+that case the return value indicates that it is already protected.
+
+sys_arch_protect() is only required if your port is supporting an operating
+system.
+
+- void sys_arch_unprotect(sys_prot_t pval)
+
+This optional function does a "fast" set of critical region protection to the
+value specified by pval. See the documentation for sys_arch_protect() for
+more information. This function is only required if your port is supporting
+an operating system.
+
+
+