* RTL_CONTEXT_foo is originally intended to be used for performance
  measurement, but mostly unused right now
* however its macros are sprinkled all over the codebase and might
  provide good help for ad-hoc debugging, and prevent SAL_INFO
  duplication
* if there is no performance logging, these macros are now forwarded to
  SAL_INFO with logarea "logfile" or "$AREA.logfile"

Change-Id: I495c8924e5b55124f7eac68eccda074d0740c117
Reviewed-on: https://gerrit.libreoffice.org/3421Reviewed-by: Björn Michaelsen <bjoern.michaelsen@canonical.com>
Tested-by: Björn Michaelsen <bjoern.michaelsen@canonical.com>