blake2: add missing <config.h>
blake2: add missing <config.h>

potatogim/librsync,yrgoldteeth/librsync,binondord/librsync,sourcefrog/librsync,agrandville/librsync,sourcefrog/librsync,potatogim/librsync,dbaarda/librsync,agrandville/librsync,librsync/librsync,binondord/librsync,binondord/librsync,potatogim/librsync,sourcefrog/librsync,Salamek/librsync,agrandville/librsync,yrgoldteeth/librsync,librsync/librsync,librsync/librsync,librsync/librsync,yrgoldteeth/librsync,dbaarda/librsync,yrgoldteeth/librsync,Salamek/librsync,Salamek/librsync,dbaarda/librsync,sourcefrog/librsync,dbaarda/librsync