Hi,

this no-functional-changes patch improves comments in 
pass_tree_loop_init::execute.

For the discussion related to the comment for scev_initialize, see:
- https://gcc.gnu.org/ml/gcc-patches/2013-02/msg01127.html
- https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56426

OK for trunk?

Thanks,
- Tom