If timestamps are enabled when logging GDB remote packets ("log enable -T -f...

If timestamps are enabled when logging GDB remote packets ("log enable -T -f /tmp/packets.log gdb-remote logs") then get the amount of time spent executing each packet and summarize at the end of a dump. Sample timing output looks like:

----------------------------------------------------------------------
Packet timing summary:
----------------------------------------------------------------------
Packet                 Time       %
---------------------- -------- ------
       qThreadStopInfo 0.363844  35.35
                     m 0.281967  27.39
                     s 0.147160  14.30
          qfThreadInfo 0.070865   6.88
          qsThreadInfo 0.061608   5.99
                     z 0.036796   3.57
                     Z 0.036271   3.52
                     c 0.018410   1.79
                     H 0.012418   1.21
---------------------- -------- ------
                 Total 1.029339 100.00

llvm-svn: 148983