gnrc_ipv6: make IPv6 dependencies optional
gnrc_ipv6: make IPv6 dependencies optional

aeneby/RIOT,MonsterCode8000/RIOT,MarkXYang/RIOT,Hyungsin/RIOT-OS,dkm/RIOT,latsku/RIOT,abkam07/RIOT,stevenj/RIOT,backenklee/RIOT,ant9000/RIOT,kYc0o/RIOT,plushvoxel/RIOT,miri64/RIOT,RubikonAlpha/RIOT,ks156/RIOT,BytesGalore/RIOT,patkan/RIOT,Yonezawa-T2/RIOT,automote/RIOT,rajma996/RIOT,adjih/RIOT,stevenj/RIOT,MarkXYang/RIOT,l3nko/RIOT,stevenj/RIOT,patkan/RIOT,gebart/RIOT,asanka-code/RIOT,hamilton-mote/RIOT-OS,dhruvvyas90/RIOT,Yonezawa-T2/RIOT,kbumsik/RIOT,RIOT-OS/RIOT,ant9000/RIOT,biboc/RIOT,d00616/RIOT,syin2/RIOT,zhuoshuguo/RIOT,gebart/RIOT,hamilton-mote/RIOT-OS,ThanhVic/RIOT,rajma996/RIOT,dailab/RIOT,ks156/RIOT,attdona/RIOT,jfischer-phytec-iot/RIOT,rajma996/RIOT,RubikonAlpha/RIOT,herrfz/RIOT,automote/RIOT,A-Paul/RIOT,backenklee/RIOT,kYc0o/RIOT,arvindpdmn/RIOT,gautric/RIOT,adjih/RIOT,MohmadAyman/RIOT,cladmi/RIOT,neumodisch/RIOT,msolters/RIOT,khhhh/RIOT,luciotorre/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,FrancescoErmini/RIOT,binarylemon/RIOT,alex1818/RIOT,khhhh/RIOT,daniel-k/RIOT,smlng/RIOT,kYc0o/RIOT,OlegHahm/RIOT,ThanhVic/RIOT,LudwigOrtmann/RIOT,thiagohd/RIOT,biboc/RIOT,x3ro/RIOT,patkan/RIOT,abp719/RIOT,immesys/RiSyn,openkosmosorg/RIOT,plushvoxel/RIOT,attdona/RIOT,EmuxEvans/RIOT,alex1818/RIOT,yogo1212/RIOT,mtausig/RIOT,mtausig/RIOT,thiagohd/RIOT,attdona/RIOT,gbarnett/RIOT,rfuentess/RIOT,beurdouche/RIOT,TobiasFredersdorf/RIOT,aeneby/RIOT,rajma996/RIOT,attdona/RIOT,yogo1212/RIOT,beurdouche/RIOT,kbumsik/RIOT,beurdouche/RIOT,DipSwitch/RIOT,DipSwitch/RIOT,yogo1212/RIOT,Osblouf/RIOT,shady33/RIOT,OTAkeys/RIOT,Josar/RIOT,khhhh/RIOT,dhruvvyas90/RIOT,BytesGalore/RIOT,stevenj/RIOT,wentaoshang/RIOT,luciotorre/RIOT,arvindpdmn/RIOT,openkosmosorg/RIOT,ant9000/RIOT,dkm/RIOT,basilfx/RIOT,RIOT-OS/RIOT,ThanhVic/RIOT,adrianghc/RIOT,immesys/RiSyn,kerneltask/RIOT,rajma996/RIOT,gebart/RIOT,avmelnikoff/RIOT,asanka-code/RIOT,lebrush/RIOT,LudwigKnuepfer/RIOT,syin2/RIOT,automote/RIOT,alex1818/RIOT,kerneltask/RIOT,robixnai/RIOT,RBartz/RIOT,asanka-code/RIOT,asanka-code/RIOT,robixnai/RIOT,luciotorre/RIOT,herrfz/RIOT,rousselk/RIOT,Lexandro92/RIOT-CoAP,thomaseichinger/RIOT,brettswann/RIOT,latsku/RIOT,adrianghc/RIOT,alex1818/RIOT,BytesGalore/RIOT,jbeyerstedt/RIOT-OTA-update,haoyangyu/RIOT,msolters/RIOT,stevenj/RIOT,OlegHahm/RIOT,binarylemon/RIOT,EmuxEvans/RIOT,mziegert/RIOT,shady33/RIOT,RIOT-OS/RIOT,toonst/RIOT,d00616/RIOT,abp719/RIOT,dkm/RIOT,MarkXYang/RIOT,cladmi/RIOT,Josar/RIOT,RIOT-OS/RIOT,jremmert-phytec-iot/RIOT,abkam07/RIOT,attdona/RIOT,hamilton-mote/RIOT-OS,dhruvvyas90/RIOT,luciotorre/RIOT,OlegHahm/RIOT,brettswann/RIOT,jremmert-phytec-iot/RIOT,abp719/RIOT,neiljay/RIOT,l3nko/RIOT,kaspar030/RIOT,avmelnikoff/RIOT,gebart/RIOT,basilfx/RIOT,RBartz/RIOT,msolters/RIOT,authmillenon/RIOT,tfar/RIOT,d00616/RIOT,rakendrathapa/RIOT,Ell-i/RIOT,arvindpdmn/RIOT,MonsterCode8000/RIOT,mfrey/RIOT,dhruvvyas90/RIOT,rousselk/RIOT,FrancescoErmini/RIOT,automote/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,haoyangyu/RIOT,dhruvvyas90/RIOT,TobiasFredersdorf/RIOT,kaspar030/RIOT,Yonezawa-T2/RIOT,abp719/RIOT,katezilla/RIOT,OlegHahm/RIOT,jasonatran/RIOT,FrancescoErmini/RIOT,neiljay/RIOT,RubikonAlpha/RIOT,avmelnikoff/RIOT,patkan/RIOT,mtausig/RIOT,MonsterCode8000/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,shady33/RIOT,rfuentess/RIOT,arvindpdmn/RIOT,lebrush/RIOT,mziegert/RIOT,gautric/RIOT,LudwigOrtmann/RIOT,brettswann/RIOT,ntrtrung/RIOT,wentaoshang/RIOT,JensErdmann/RIOT,alex1818/RIOT,LudwigKnuepfer/RIOT,ks156/RIOT,kaleb-himes/RIOT,Lexandro92/RIOT-CoAP,jfischer-phytec-iot/RIOT,neumodisch/RIOT,Ell-i/RIOT,gbarnett/RIOT,x3ro/RIOT,kaspar030/RIOT,brettswann/RIOT,ntrtrung/RIOT,kbumsik/RIOT,biboc/RIOT,josephnoir/RIOT,adjih/RIOT,x3ro/RIOT,adjih/RIOT,ks156/RIOT,MonsterCode8000/RIOT,RIOT-OS/RIOT,Osblouf/RIOT,adrianghc/RIOT,rousselk/RIOT,daniel-k/RIOT,DipSwitch/RIOT,arvindpdmn/RIOT,katezilla/RIOT,zhuoshuguo/RIOT,thiagohd/RIOT,Josar/RIOT,watr-li/RIOT,LudwigKnuepfer/RIOT,backenklee/RIOT,mtausig/RIOT,JensErdmann/RIOT,daniel-k/RIOT,malosek/RIOT,basilfx/RIOT,robixnai/RIOT,immesys/RiSyn,patkan/RIOT,rakendrathapa/RIOT,daniel-k/RIOT,dailab/RIOT,gbarnett/RIOT,toonst/RIOT,khhhh/RIOT,wentaoshang/RIOT,thomaseichinger/RIOT,BytesGalore/RIOT,kerneltask/RIOT,A-Paul/RIOT,daniel-k/RIOT,msolters/RIOT,jremmert-phytec-iot/RIOT,roberthartung/RIOT,jfischer-phytec-iot/RIOT,miri64/RIOT,kb2ma/RIOT,luciotorre/RIOT,OlegHahm/RIOT,yogo1212/RIOT,Osblouf/RIOT,mfrey/RIOT,LudwigOrtmann/RIOT,jasonatran/RIOT,shady33/RIOT,authmillenon/RIOT,neiljay/RIOT,mziegert/RIOT,Osblouf/RIOT,toonst/RIOT,RBartz/RIOT,dhruvvyas90/RIOT,adjih/RIOT,mziegert/RIOT,binarylemon/RIOT,roberthartung/RIOT,miri64/RIOT,zhuoshuguo/RIOT,l3nko/RIOT,Lexandro92/RIOT-CoAP,cladmi/RIOT,attdona/RIOT,A-Paul/RIOT,Hyungsin/RIOT-OS,RubikonAlpha/RIOT,latsku/RIOT,altairpearl/RIOT,zhuoshuguo/RIOT,gebart/RIOT,toonst/RIOT,MarkXYang/RIOT,watr-li/RIOT,rousselk/RIOT,dkm/RIOT,EmuxEvans/RIOT,Hyungsin/RIOT-OS,LudwigOrtmann/RIOT,kYc0o/RIOT,miri64/RIOT,adrianghc/RIOT,kb2ma/RIOT,hamilton-mote/RIOT-OS,basilfx/RIOT,kerneltask/RIOT,jbeyerstedt/RIOT-OTA-update,MohmadAyman/RIOT,mfrey/RIOT,authmillenon/RIOT,Ell-i/RIOT,haoyangyu/RIOT,Yonezawa-T2/RIOT,neumodisch/RIOT,ant9000/RIOT,JensErdmann/RIOT,JensErdmann/RIOT,BytesGalore/RIOT,backenklee/RIOT,beurdouche/RIOT,kerneltask/RIOT,alignan/RIOT,abp719/RIOT,thomaseichinger/RIOT,wentaoshang/RIOT,shady33/RIOT,aeneby/RIOT,yogo1212/RIOT,latsku/RIOT,watr-li/RIOT,LudwigKnuepfer/RIOT,MonsterCode8000/RIOT,msolters/RIOT,immesys/RiSyn,TobiasFredersdorf/RIOT,katezilla/RIOT,ThanhVic/RIOT,neumodisch/RIOT,openkosmosorg/RIOT,gbarnett/RIOT,thiagohd/RIOT,abkam07/RIOT,katezilla/RIOT,herrfz/RIOT,alignan/RIOT,lazytech-org/RIOT,MohmadAyman/RIOT,aeneby/RIOT,kb2ma/RIOT,lebrush/RIOT,jasonatran/RIOT,latsku/RIOT,DipSwitch/RIOT,alignan/RIOT,khhhh/RIOT,TobiasFredersdorf/RIOT,smlng/RIOT,A-Paul/RIOT,miri64/RIOT,mziegert/RIOT,jbeyerstedt/RIOT-OTA-update,robixnai/RIOT,tfar/RIOT,zhuoshuguo/RIOT,RBartz/RIOT,cladmi/RIOT,rousselk/RIOT,mfrey/RIOT,jremmert-phytec-iot/RIOT,MonsterCode8000/RIOT,authmillenon/RIOT,alignan/RIOT,lazytech-org/RIOT,kb2ma/RIOT,malosek/RIOT,FrancescoErmini/RIOT,JensErdmann/RIOT,rajma996/RIOT,FrancescoErmini/RIOT,RBartz/RIOT,backenklee/RIOT,Lexandro92/RIOT-CoAP,rfuentess/RIOT,RBartz/RIOT,plushvoxel/RIOT,x3ro/RIOT,l3nko/RIOT,binarylemon/RIOT,syin2/RIOT,ntrtrung/RIOT,RubikonAlpha/RIOT,kYc0o/RIOT,altairpearl/RIOT,yogo1212/RIOT,jremmert-phytec-iot/RIOT,robixnai/RIOT,Yonezawa-T2/RIOT,abp719/RIOT,jfischer-phytec-iot/RIOT,mziegert/RIOT,rfuentess/RIOT,tfar/RIOT,lebrush/RIOT,gbarnett/RIOT,lebrush/RIOT,Lexandro92/RIOT-CoAP,asanka-code/RIOT,rakendrathapa/RIOT,josephnoir/RIOT,Josar/RIOT,aeneby/RIOT,d00616/RIOT,alignan/RIOT,brettswann/RIOT,immesys/RiSyn,altairpearl/RIOT,malosek/RIOT,kb2ma/RIOT,automote/RIOT,authmillenon/RIOT,automote/RIOT,syin2/RIOT,biboc/RIOT,cladmi/RIOT,herrfz/RIOT,haoyangyu/RIOT,ntrtrung/RIOT,jasonatran/RIOT,EmuxEvans/RIOT,openkosmosorg/RIOT,LudwigKnuepfer/RIOT,MarkXYang/RIOT,x3ro/RIOT,roberthartung/RIOT,EmuxEvans/RIOT,OTAkeys/RIOT,ntrtrung/RIOT,openkosmosorg/RIOT,gbarnett/RIOT,thiagohd/RIOT,abkam07/RIOT,DipSwitch/RIOT,Yonezawa-T2/RIOT,abkam07/RIOT,basilfx/RIOT,josephnoir/RIOT,josephnoir/RIOT,luciotorre/RIOT,smlng/RIOT,rakendrathapa/RIOT,JensErdmann/RIOT,zhuoshuguo/RIOT,rakendrathapa/RIOT,jfischer-phytec-iot/RIOT,Ell-i/RIOT,shady33/RIOT,roberthartung/RIOT,tfar/RIOT,ant9000/RIOT,haoyangyu/RIOT,kbumsik/RIOT,FrancescoErmini/RIOT,neiljay/RIOT,dailab/RIOT,haoyangyu/RIOT,lazytech-org/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,gautric/RIOT,l3nko/RIOT,plushvoxel/RIOT,binarylemon/RIOT,watr-li/RIOT,kaleb-himes/RIOT,neumodisch/RIOT,roberthartung/RIOT,msolters/RIOT,thomaseichinger/RIOT,thomaseichinger/RIOT,ThanhVic/RIOT,daniel-k/RIOT,ks156/RIOT,thiagohd/RIOT,altairpearl/RIOT,herrfz/RIOT,lazytech-org/RIOT,biboc/RIOT,lebrush/RIOT,OTAkeys/RIOT,neumodisch/RIOT,A-Paul/RIOT,arvindpdmn/RIOT,d00616/RIOT,syin2/RIOT,LudwigOrtmann/RIOT,plushvoxel/RIOT,d00616/RIOT,Ell-i/RIOT,watr-li/RIOT,rousselk/RIOT,lazytech-org/RIOT,TobiasFredersdorf/RIOT,jremmert-phytec-iot/RIOT,smlng/RIOT,asanka-code/RIOT,latsku/RIOT,openkosmosorg/RIOT,binarylemon/RIOT,rakendrathapa/RIOT,herrfz/RIOT,abkam07/RIOT,DipSwitch/RIOT,patkan/RIOT,stevenj/RIOT,LudwigOrtmann/RIOT,toonst/RIOT,kaspar030/RIOT,mtausig/RIOT,gautric/RIOT,immesys/RiSyn,dkm/RIOT,malosek/RIOT,authmillenon/RIOT,Osblouf/RIOT,neiljay/RIOT,kaleb-himes/RIOT,gautric/RIOT,beurdouche/RIOT,adrianghc/RIOT,katezilla/RIOT,MohmadAyman/RIOT,brettswann/RIOT,avmelnikoff/RIOT,Hyungsin/RIOT-OS,alex1818/RIOT,josephnoir/RIOT,kaspar030/RIOT,l3nko/RIOT,ntrtrung/RIOT,kbumsik/RIOT,EmuxEvans/RIOT,rfuentess/RIOT,malosek/RIOT,RubikonAlpha/RIOT,wentaoshang/RIOT,jbeyerstedt/RIOT-OTA-update,OTAkeys/RIOT,mfrey/RIOT,avmelnikoff/RIOT,jasonatran/RIOT,kaleb-himes/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,khhhh/RIOT,ThanhVic/RIOT,Osblouf/RIOT,MohmadAyman/RIOT,wentaoshang/RIOT,smlng/RIOT,tfar/RIOT,Hyungsin/RIOT-OS,OTAkeys/RIOT,watr-li/RIOT,MarkXYang/RIOT,dailab/RIOT,jbeyerstedt/RIOT-OTA-update,altairpearl/RIOT,hamilton-mote/RIOT-OS,Lexandro92/RIOT-CoAP,robixnai/RIOT,malosek/RIOT,kaleb-himes/RIOT,Josar/RIOT,altairpearl/RIOT,dailab/RIOT,MohmadAyman/RIOT