Remove the remnants of the legacy trace functionality (since replaced with FreeRTOS+Trace).

Replaced the #error that traps configMAX_SYSCALL_INTERRUPT_PRIORITY being set to 0 with a configASSERT() for GCC Cortex-M3/4 ports as the #error does not work if configMAX_SYSCALL_INTERRUPT_PRIORITY includes any casting.  Not a problem for other compilers as they cannot have casting anyway as that would break the assembly code.

FreeRTOS/Source/portable/MemMang/heap_1.c

@@ -146,6 +146,9 @@ void vPortFree( void *pv )
 	heap_4.c for alternative implementations, and the memory management pages of 
 	http://www.FreeRTOS.org for more information. */
 	( void ) pv;
+	
+	/* Force an assert as it is invalid to call this function. */
+	configASSERT( pv == NULL );
 }
 /*-----------------------------------------------------------*/