added test for lw ra; jr ra (with files)

cMIPS/tests/jallwjr.expected

+00000028
+00000002
+00000028
+00000004
+00000028
+00000008
+00000028
+00000010
+00000028
+00000020
+00000028
+00000040
+00000028
+00000080

cMIPS/tests/jallwjr.s

+	.include "cMIPS.s"
+	.text
+	.align 2
+	.set noat
+	.set noreorder
+	.globl _start
+	.ent _start
+	
+_start: nop
+	la $15,x_IO_BASE_ADDR
+	li $3,1
+	li $4,5
+	la $29, (x_DATA_BASE_ADDR + 1024)	# space for stack
+	
+	li  $9,1
+	li  $19, 100
+	
+itera:	jal fun
+	sw   $31, 0($15) # $31 <- 0,fun+4
+	slt  $18, $9, $19
+        bne  $18, $0, itera
+	nop
+	j    end
+	nop
+
+fun:	addiu $sp, $sp, -8
+	sw    $ra, 0($sp)
+	add   $9, $9, $9
+	move  $ra, $zero
+	addiu $sp, $sp, +8
+	lw    $ra, -8($sp)
+	jr    $ra
+	sw    $9, 0($15)
+
+	
+end:	nop
+	nop
+	nop
+	nop
+	nop
+	wait 
+	nop
+	nop
+	.end _start