COMP: Fixed warnings about signess comparison.
COMP: Fixed warnings about signess comparison.

The > 0 comparison of this filter should have been using the
NumericTraits< TInput >::Zero, instead of the plain "0" symbol.
Correspondingly, the concept check for ">" should be between
InputPixelType and InputPixelType, not versus "int".

This was generating a large number of warnings when building
SimpleITK, due to the variety of instantiations, that expose
the inconsitency of the itkAbsImageFilter types.

The computation of ABS now uses vnl_math_abs() that is an
specialized inlined function.

Change-Id: Ib1742c10abd91e101604d03df568f372c59e6707

BRAINSia/ITK,jcfr/ITK,fuentesdt/InsightToolkit-dev,paulnovo/ITK,vfonov/ITK,spinicist/ITK,ajjl/ITK,PlutoniumHeart/ITK,itkvideo/ITK,richardbeare/ITK,zachary-williamson/ITK,fbudin69500/ITK,biotrump/ITK,msmolens/ITK,spinicist/ITK,richardbeare/ITK,LucasGandel/ITK,spinicist/ITK,wkjeong/ITK,fbudin69500/ITK,ajjl/ITK,rhgong/itk-with-dom,BRAINSia/ITK,atsnyder/ITK,eile/ITK,wkjeong/ITK,jmerkow/ITK,biotrump/ITK,malaterre/ITK,daviddoria/itkHoughTransform,biotrump/ITK,fuentesdt/InsightToolkit-dev,daviddoria/itkHoughTransform,stnava/ITK,spinicist/ITK,CapeDrew/DCMTK-ITK,BlueBrain/ITK,wkjeong/ITK,PlutoniumHeart/ITK,biotrump/ITK,BlueBrain/ITK,cpatrick/ITK-RemoteIO,daviddoria/itkHoughTransform,hinerm/ITK,thewtex/ITK,malaterre/ITK,stnava/ITK,atsnyder/ITK,spinicist/ITK,eile/ITK,thewtex/ITK,fbudin69500/ITK,heimdali/ITK,vfonov/ITK,biotrump/ITK,daviddoria/itkHoughTransform,fedral/ITK,GEHC-Surgery/ITK,paulnovo/ITK,richardbeare/ITK,atsnyder/ITK,InsightSoftwareConsortium/ITK,atsnyder/ITK,hinerm/ITK,malaterre/ITK,CapeDrew/DCMTK-ITK,zachary-williamson/ITK,GEHC-Surgery/ITK,GEHC-Surgery/ITK,cpatrick/ITK-RemoteIO,InsightSoftwareConsortium/ITK,malaterre/ITK,daviddoria/itkHoughTransform,malaterre/ITK,heimdali/ITK,eile/ITK,rhgong/itk-with-dom,heimdali/ITK,stnava/ITK,Kitware/ITK,wkjeong/ITK,InsightSoftwareConsortium/ITK,jcfr/ITK,BlueBrain/ITK,rhgong/itk-with-dom,cpatrick/ITK-RemoteIO,vfonov/ITK,zachary-williamson/ITK,InsightSoftwareConsortium/ITK,hjmjohnson/ITK,Kitware/ITK,BlueBrain/ITK,cpatrick/ITK-RemoteIO,CapeDrew/DITK,CapeDrew/DITK,BRAINSia/ITK,CapeDrew/DITK,heimdali/ITK,hinerm/ITK,BlueBrain/ITK,BRAINSia/ITK,zachary-williamson/ITK,zachary-williamson/ITK,LucasGandel/ITK,stnava/ITK,cpatrick/ITK-RemoteIO,CapeDrew/DITK,malaterre/ITK,rhgong/itk-with-dom,spinicist/ITK,hinerm/ITK,jcfr/ITK,eile/ITK,vfonov/ITK,GEHC-Surgery/ITK,zachary-williamson/ITK,eile/ITK,malaterre/ITK,hjmjohnson/ITK,jmerkow/ITK,jcfr/ITK,BRAINSia/ITK,fuentesdt/InsightToolkit-dev,CapeDrew/DCMTK-ITK,fuentesdt/InsightToolkit-dev,atsnyder/ITK,hjmjohnson/ITK,jcfr/ITK,atsnyder/ITK,spinicist/ITK,vfonov/ITK,LucasGandel/ITK,fedral/ITK,richardbeare/ITK,LucasGandel/ITK,Kitware/ITK,hendradarwin/ITK,spinicist/ITK,fedral/ITK,LucHermitte/ITK,wkjeong/ITK,fbudin69500/ITK,LucHermitte/ITK,ajjl/ITK,jcfr/ITK,LucasGandel/ITK,heimdali/ITK,itkvideo/ITK,CapeDrew/DCMTK-ITK,hjmjohnson/ITK,PlutoniumHeart/ITK,CapeDrew/DCMTK-ITK,blowekamp/ITK,heimdali/ITK,Kitware/ITK,CapeDrew/DCMTK-ITK,BlueBrain/ITK,stnava/ITK,Kitware/ITK,CapeDrew/DITK,malaterre/ITK,itkvideo/ITK,zachary-williamson/ITK,rhgong/itk-with-dom,blowekamp/ITK,eile/ITK,blowekamp/ITK,PlutoniumHeart/ITK,msmolens/ITK,spinicist/ITK,LucasGandel/ITK,eile/ITK,richardbeare/ITK,daviddoria/itkHoughTransform,itkvideo/ITK,blowekamp/ITK,fbudin69500/ITK,ajjl/ITK,GEHC-Surgery/ITK,PlutoniumHeart/ITK,msmolens/ITK,GEHC-Surgery/ITK,fedral/ITK,hinerm/ITK,Kitware/ITK,paulnovo/ITK,jmerkow/ITK,PlutoniumHeart/ITK,jcfr/ITK,itkvideo/ITK,jcfr/ITK,hinerm/ITK,eile/ITK,jmerkow/ITK,hendradarwin/ITK,GEHC-Surgery/ITK,stnava/ITK,jmerkow/ITK,LucHermitte/ITK,LucHermitte/ITK,CapeDrew/DCMTK-ITK,CapeDrew/DITK,itkvideo/ITK,BlueBrain/ITK,heimdali/ITK,CapeDrew/DCMTK-ITK,itkvideo/ITK,hendradarwin/ITK,zachary-williamson/ITK,thewtex/ITK,hjmjohnson/ITK,paulnovo/ITK,msmolens/ITK,cpatrick/ITK-RemoteIO,blowekamp/ITK,BRAINSia/ITK,ajjl/ITK,fuentesdt/InsightToolkit-dev,daviddoria/itkHoughTransform,wkjeong/ITK,BlueBrain/ITK,cpatrick/ITK-RemoteIO,msmolens/ITK,hinerm/ITK,InsightSoftwareConsortium/ITK,LucHermitte/ITK,ajjl/ITK,PlutoniumHeart/ITK,eile/ITK,msmolens/ITK,itkvideo/ITK,jmerkow/ITK,hjmjohnson/ITK,CapeDrew/DITK,malaterre/ITK,LucHermitte/ITK,LucHermitte/ITK,fedral/ITK,hjmjohnson/ITK,ajjl/ITK,paulnovo/ITK,stnava/ITK,CapeDrew/DCMTK-ITK,fuentesdt/InsightToolkit-dev,thewtex/ITK,CapeDrew/DITK,fuentesdt/InsightToolkit-dev,hendradarwin/ITK,wkjeong/ITK,fbudin69500/ITK,PlutoniumHeart/ITK,paulnovo/ITK,hendradarwin/ITK,LucasGandel/ITK,thewtex/ITK,ajjl/ITK,zachary-williamson/ITK,daviddoria/itkHoughTransform,jmerkow/ITK,blowekamp/ITK,rhgong/itk-with-dom,LucasGandel/ITK,jmerkow/ITK,heimdali/ITK,vfonov/ITK,hendradarwin/ITK,paulnovo/ITK,InsightSoftwareConsortium/ITK,hinerm/ITK,hendradarwin/ITK,LucHermitte/ITK,blowekamp/ITK,stnava/ITK,fedral/ITK,fedral/ITK,atsnyder/ITK,stnava/ITK,itkvideo/ITK,hendradarwin/ITK,richardbeare/ITK,cpatrick/ITK-RemoteIO,thewtex/ITK,vfonov/ITK,blowekamp/ITK,thewtex/ITK,Kitware/ITK,fuentesdt/InsightToolkit-dev,GEHC-Surgery/ITK,wkjeong/ITK,BRAINSia/ITK,daviddoria/itkHoughTransform,vfonov/ITK,CapeDrew/DITK,hinerm/ITK,fbudin69500/ITK,atsnyder/ITK,biotrump/ITK,richardbeare/ITK,atsnyder/ITK,rhgong/itk-with-dom,rhgong/itk-with-dom,msmolens/ITK,msmolens/ITK,fuentesdt/InsightToolkit-dev,fbudin69500/ITK,biotrump/ITK,paulnovo/ITK,InsightSoftwareConsortium/ITK,biotrump/ITK,fedral/ITK,vfonov/ITK