* Added new operator replacing the former alias to setzaxis
* Fixed documentation for setzaxis
* Re-factored operator argument evaluation for Selvar module

* r3931: Mastrfu: Merge declaration and definition
* r3930: renamed vinterp to after_vertint
* r3929: renamed legendre.c to after_sptrans.c
* r3928: renamed fouriertrans.c to after_fctrans.c
* r3927: Select: abort if no timestep is seleced
* r3926: Seltime: Merge declaration and definition
* r3925: Seltime: abort if no timestep is seleced
* r3924: specspace: Merge declaration and definition
* r3923: added Afterburner.c
* r3922: added Afterburner.c

* r3920: legendre.c: removed unused include
* r3919: added compare.h
* r3918: set revision number to 1.6.9rc1
* r3917: test/grid_search: update to YAC version 1.0.3
* r3916: clipping: update to YAC version 1.0.3
* r3915: Merge: Merge declaration and definition
* r3914: Vertintml: added default level
* r3913: ChangeLog: update
* r3912: fix typo
* r3911: Fldstat: added parameter noweights to use constant grid cell area weights
* r3910: change cdi svn:external to trunk/cdi (masked by local change)

* r3908: expr docu update
* r3907: setpartab doc: added parameter convert in example
* r3906: expr: added support for operator ?:,&&,||
* r3905: gradsdes: removed support for option 360_day_calendar
* r3904: gradsdes: added support for option 360_day_calendar
* r3902: change cdi svn:external to tags/cdi-1.6.8
* r3901: expr: added support for operator ?: (short ifelse)
* r3900: eof, eofcoeff: docu update
* r3899: eof, eof3d: use area weights instead of no weights
* r3898: Vertstat cleanup
* r3897: Docu update
* r3896: Docu update
* r3895: vertmean, vertavg: changed to weighted means if layer bounds are available