Enhance the call tree to display IPC information if it is available.

Committer testing:

[acme@quaco adrian.hunter]$ python ~acme/libexec/perf-core/scripts/python/exported-sql-viewer.py ~/c/adrian.hunter/simple-retpoline.db

Reports -> Call Tree, then expand a few trees, then select with the
mouse and press control+C (copy):

Call Path                   Object        Call Time Time  Time(%) Insn  Insn   Cyc   Cyc   IPC Branch Branch
▼ simple-retpolin                                   (ns)          Cnt   Cnt(%) Cnt   Cnt(%)     Count Count(%)
  ▼ 23003:23003
    ▼ _start                ld-2.28.so    112195670 218295 100.0 127746 100.0 207320 100.0 0.62 13046 100.0
      ▶ unknown             unknown       112195987   3202   1.5      0   0.0      0   0.0    0     1   0.0
      ▶ _dl_start           ld-2.28.so    112199189 188471  86.3 123394  96.6 180007  86.8 0.69 12529  96.0
      ▼ _dl_init            ld-2.28.so    112387660  13406   6.1   3207   2.5  14868   7.2 0.22   327   2.5
        ▶ call_init.part.0  ld-2.28.so    112387773    117   0.9     70   2.2    639   4.3 0.11     3   0.9
        ▶ call_init.part.0  ld-2.28.so    112387890  13129  97.9   3103  96.8  14100  94.8 0.22   315  96.3
        ▶ call_init.part.0  ld-2.28.so    112401020      0   0.0      0   0.0      0   0.0    0     2   0.6
      ▼ _start              simple-retpol 112401066  12899   5.9   1142   0.9  11561   5.6 0.10   184   1.4
        ▶ unknown           unknown       112401388    846   6.6      0   0.0      0   0.0    0     1   0.5
        ▼ __libc_start_main libc-2.28.so  112402344  11621  90.1   1129  98.9  10350  89.5 0.11   181  98.4
          ▶ __cxa_atexit    libc-2.28.so  112402360   2302  19.8    101   8.9   1817  17.6 0.06    13   7.2
          ▶ __libc_csu_init simple-retpol 112404673    121   1.0     43   3.8    340   3.3 0.13     8   4.4
          ▶ _setjmp         libc-2.28.so  112404794     74   0.6     46   4.1    206   2.0 0.22     4   2.2
          ▼ main            simple-retpol 112404892     44   0.4     23   2.0    126   1.2 0.18    12   6.6
            ▼ foo           simple-retpol 112404892     19  43.2     12  52.2     55  43.7 0.22     5  41.7
                bar         simple-retpol 112404896     12  63.2      3  25.0     34  61.8 0.09     1  20.0
            ▼ foo           simple-retpol 112404911     25  56.8     11  47.8     71  56.3 0.15     5  41.7
              ▶ bar         simple-retpol 112404924     10  40.0      3  27.3     27  38.0 0.11     1  20.0
          ▶ exit            libc-2.28.so  112404936   9029  77.7    878  77.8   7765  75.0 0.11   139  76.8
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20190520113728.14389-22-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>