COMP: Add missing include <stddef.h> for ptrdiff_t
COMP: Add missing include <stddef.h> for ptrdiff_t

Fixes error "ptrdiff_t was not declared in this scope".

Reported-by: Dominique Belhachemi <6822b9bc66fb9be78149a00f8455c7e93ee5d5bc@debian.org>

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