Ensure the first task starts with interrupts enabled.

Source/portable/RVDS/ARM_CM3/port.c

@@ -129,6 +129,8 @@ __asm void vPortSVCHandler( void )
 	ldr r2, =uxCriticalNesting	/* Restore the critical nesting count used by the task. */
 	str r1, [r2]				
 	msr psp, r0					/* Restore the task stack pointer. */
+	mov r0, #0
+	msr	basepri, r0
 	orr r14, #0xd				
 	bx r14						
 }