0.0.6:
  - order quals and constants by their text positions.
  - fix bug with Index-Only Scans, which where not correctly supported
  - make pg_config configurable from the make invocation
  - ensure pg_qualstats is in shared_preload_libraries
0.0.5:
  - fix bug with = ANY(NULL) expressions
0.0.4:
 - add inline documentation in the sql script
 - fix a bug with 32bits builds (thanks to Alain Delorme for reporting it)