Added S2G times + fixed up -X output to include X2X

Including Q2Q, Q2G, S2G, G2I, Q2M, I2D, M2D, D2C, Q2C.

S2G is part of Q2G, and shows the number of times we had to sleep to get a request.

Ignored 0-byte I/Os - coming from barrier I/Os...

---
 btt/bt_timeline.c    |    2 +-
 btt/doc/btt.tex      |   38 ++++++++++++++++++++++++++++++--------
 btt/globals.h        |    8 ++++++--
 btt/inlines.h        |    5 +++++
 btt/output.c         |   42 +++++++++++++++++++++++++++---------------
 btt/trace.c          |    1 +
 btt/trace_complete.c |    3 +++
 btt/trace_im.c       |   36 +++++++++++++++++++++++++++++++-----
 btt/trace_issue.c    |    4 ++++
 btt/trace_queue.c    |    3 +++
 10 files changed, 111 insertions(+), 31 deletions(-)