Use 99th percentile as the maximum frequency when adjusting icon color

When adjusting the icon color according to frequency, compute the 99th
percentile of all measured frequencies and use it as the "true" maximum
frequency. This is required because in a small percentage of cases the
current CPU frequency reported by Linux can be unrealistic, for example
4.59 GHz on a CPU that has an actual maximum frequency of about 4.4 GHz.
2 jobs for !33 with 99 in 1 minute and 6 seconds
latest detached
Status Job ID Name Coverage
  Build
passed #11855
build

00:00:26

 
  Distcheck
passed #11856
distcheck

00:00:40