sys/newlib: Add missing syscalls (stubs).
sys/newlib: Add missing syscalls (stubs).

Add small stubs for _times_r and _link_r so that code using times()
or link() can still compile. The functions are marked as not implemented
and return invalid codes.

OlegHahm/RIOT,authmillenon/RIOT,yogo1212/RIOT,biboc/RIOT,cladmi/RIOT,OlegHahm/RIOT,A-Paul/RIOT,cladmi/RIOT,smlng/RIOT,gebart/RIOT,josephnoir/RIOT,neiljay/RIOT,BytesGalore/RIOT,kYc0o/RIOT,josephnoir/RIOT,A-Paul/RIOT,basilfx/RIOT,kbumsik/RIOT,avmelnikoff/RIOT,RIOT-OS/RIOT,basilfx/RIOT,avmelnikoff/RIOT,cladmi/RIOT,smlng/RIOT,gebart/RIOT,biboc/RIOT,gebart/RIOT,kbumsik/RIOT,RIOT-OS/RIOT,smlng/RIOT,mtausig/RIOT,mfrey/RIOT,mfrey/RIOT,miri64/RIOT,RIOT-OS/RIOT,biboc/RIOT,OlegHahm/RIOT,ant9000/RIOT,kYc0o/RIOT,smlng/RIOT,miri64/RIOT,lazytech-org/RIOT,A-Paul/RIOT,josephnoir/RIOT,RIOT-OS/RIOT,aeneby/RIOT,neiljay/RIOT,toonst/RIOT,mtausig/RIOT,kYc0o/RIOT,mfrey/RIOT,lazytech-org/RIOT,kbumsik/RIOT,yogo1212/RIOT,authmillenon/RIOT,BytesGalore/RIOT,gebart/RIOT,kaspar030/RIOT,x3ro/RIOT,yogo1212/RIOT,josephnoir/RIOT,mfrey/RIOT,mtausig/RIOT,toonst/RIOT,lazytech-org/RIOT,rfuentess/RIOT,josephnoir/RIOT,RIOT-OS/RIOT,smlng/RIOT,basilfx/RIOT,OlegHahm/RIOT,mfrey/RIOT,neiljay/RIOT,x3ro/RIOT,yogo1212/RIOT,yogo1212/RIOT,basilfx/RIOT,ant9000/RIOT,BytesGalore/RIOT,rfuentess/RIOT,basilfx/RIOT,x3ro/RIOT,A-Paul/RIOT,neiljay/RIOT,lazytech-org/RIOT,biboc/RIOT,aeneby/RIOT,BytesGalore/RIOT,avmelnikoff/RIOT,cladmi/RIOT,miri64/RIOT,ant9000/RIOT,aeneby/RIOT,kaspar030/RIOT,x3ro/RIOT,jasonatran/RIOT,kbumsik/RIOT,biboc/RIOT,miri64/RIOT,jasonatran/RIOT,kYc0o/RIOT,kaspar030/RIOT,ant9000/RIOT,rfuentess/RIOT,OTAkeys/RIOT,authmillenon/RIOT,avmelnikoff/RIOT,ant9000/RIOT,yogo1212/RIOT,miri64/RIOT,x3ro/RIOT,jasonatran/RIOT,toonst/RIOT,gebart/RIOT,authmillenon/RIOT,OTAkeys/RIOT,OTAkeys/RIOT,OTAkeys/RIOT,authmillenon/RIOT,kYc0o/RIOT,neiljay/RIOT,kaspar030/RIOT,cladmi/RIOT,jasonatran/RIOT,mtausig/RIOT,rfuentess/RIOT,OlegHahm/RIOT,authmillenon/RIOT,aeneby/RIOT,rfuentess/RIOT,A-Paul/RIOT,kaspar030/RIOT,toonst/RIOT,lazytech-org/RIOT,kbumsik/RIOT,avmelnikoff/RIOT,BytesGalore/RIOT,mtausig/RIOT,OTAkeys/RIOT,jasonatran/RIOT,aeneby/RIOT,toonst/RIOT