make the loop comment printer print out a much better structured

output.  An example:

        .align  4, 0x90
LBB1_5:                                                     ## %while.cond3
                                                            ##   Parent Loop BB1_1 Depth=1
                                                            ## =>  This Loop Header: Depth=2
                                                            ##       Child Loop BB1_8 Depth 3
                                                            ##       Child Loop BB1_6 Depth 3

llvm-svn: 94225