Merge remote-tracking branch 'stefanha/tracing' into staging

* stefanha/tracing:
  tracetool: handle DTrace keywords 'in', 'next', 'self'
  tracetool: Add MAINTAINERS info
  tracetool: Add support for the 'dtrace' backend
  tracetool: Add support for the 'ust' backend
  tracetool: Add support for the 'simple' backend
  tracetool: Add support for the 'stderr' backend
  tracetool: Add module for the 'h' format
  tracetool: Add module for the 'c' format
  tracetool: Rewrite infrastructure as python modules