minor fixes on alu

cpu/alu/alu.sv

@@ -47,6 +47,7 @@ always @(*) begin
         alu_out = tmpOut;
     end
 
+    //TODO: improve this part using increment/decrement logic
     if (alu_out < 0)
         flag = 0;   // negative flag
     else if (alu_out = 0)

cpu/alu/lookahead.sv

@@ -4,14 +4,14 @@ package lookahead (
     input [15:0]b,
 );
 
-    res = and16(y, a, b);
+res = and16(y, a, b);
 
-    for (i=0; i<15 ; i=i+1)
+for (i=0; i<15 ; i=i+1)
-        if (res[i] = 0)
+    if (res[i] = 0)
-            carry_bit[i] = 0;
+        carry_bit[i] = 0;
-        else
+    else
-            carry_bit[i] = 1;
+        carry_bit[i] = 1;
-        end
     end
+end
 
 endpackage

cpu/cpu.sv

@@ -0,0 +1 @@
+import alu::*;