kvm: kvmtrace_format: add statistic section

kvm: kvmtrace_format: add statistic section

Usually people don't want to read thousands of trace log lines to interpret
the data, a condensed statistic about the traced events is usually better
to read.
This patch adds a new command line switch -s that tells kvmtrace_format to
generate statistics while processing the trace records. Those statistics are
then printed at the end of the output.
This patch contains a statistic function for the ppc instruction emulation.
An example output might look like that:

      mnemonic +      count
---------------+-----------
        wrteei |       1260
         mfmsr |        977
         mtspr |        895
         wrtee |        742
         mfspr |        534
           rfi |        179
         mtmsr |         90
           lbz |         53
           stb |         28
           sum =       4758
[...] more detailed statistics about spr, dcr and tlb usage

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>