STW phases anaysis

[krzysztofslusarski]

Hi, first of all, good work. Unfortunately your tool analyze the stop-the-world phases generated by GC. It's ok if it is your goal, but you have to remember that there are other JVM internals that needs STW. JIT for example. If you want to provide complex information you need to analyze Xlog:safepoint log. If you don't want to analyze it then it would be nice to give a clarification at the begging of the Section A.