DOC: test if ${${itk-module}_SOURCE_DIR}/include exists
DOC: test if ${${itk-module}_SOURCE_DIR}/include exists

Before adding it to DOXYGEN_INCLUDE_DIRS, we check if this directory
exists. This change should fix doxygen warnings about input paths.

see http://www.cdash.org/CDash/viewBuildError.php?type=1&buildid=1096112

Change-Id: I616791efc612489885d7d3151b2ecb5207042a6f

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