fix thumb long branch link weird sign logic

src/crab/thumb/long_branch_link.cr

@@ -3,12 +3,13 @@ module THUMB
     second_instr = bit?(instr, 11)
     offset = bits(instr, 0..10)
     if second_instr
-      @r[14] &+= (offset << 1)
-      @r[15], @r[14] = @r[14], @r[15] - 1
+      temp = @r[15] &- 2
+      @r[15] = @r[14] &+ (offset << 1)
+      @r[14] = temp | 1
       clear_pipeline
     else
-      offset = (offset << 5).to_i16! >> 5 # todo make this just bit math
-      @r[14] = @r[15] &+ (offset << 12)
+      offset = (offset << 5).to_i16! >> 5
+      @r[14] = @r[15] &+ (offset.to_u32 << 12)
     end
   end
 end