fix _need_update in gloo.variable
fix _need_update in gloo.variable

inclement/vispy,Eric89GXL/vispy,kkuunnddaannkk/vispy,sh4wn/vispy,RebeccaWPerry/vispy,michaelaye/vispy,RebeccaWPerry/vispy,michaelaye/vispy,sbtlaarzc/vispy,ghisvail/vispy,QuLogic/vispy,bollu/vispy,inclement/vispy,Eric89GXL/vispy,bollu/vispy,bollu/vispy,jay3sh/vispy,RebeccaWPerry/vispy,dchilds7/Deysha-Star-Formation,jdreaver/vispy,drufat/vispy,hronoses/vispy,jay3sh/vispy,drufat/vispy,julienr/vispy,sh4wn/vispy,drufat/vispy,sbtlaarzc/vispy,inclement/vispy,hronoses/vispy,kkuunnddaannkk/vispy,jdreaver/vispy,dchilds7/Deysha-Star-Formation,Eric89GXL/vispy,QuLogic/vispy,ghisvail/vispy,hronoses/vispy,srinathv/vispy,sh4wn/vispy,dchilds7/Deysha-Star-Formation,QuLogic/vispy,srinathv/vispy,ghisvail/vispy,michaelaye/vispy,kkuunnddaannkk/vispy,julienr/vispy,sbtlaarzc/vispy,jay3sh/vispy,srinathv/vispy,julienr/vispy,jdreaver/vispy