Fix drag/drop on IE9
Fix drag/drop on IE9

Closes #857

rustemferreira/CodeMirror,rasata/CodeMirror,jpolitz/CodeMirror,cintiamh/CodeMirror,sekcheong/CodeMirror,KamranMackey/CodeMirror,tpphu/CodeMirror,Ermlab/CodeMirror,MarcelGerber/CodeMirror,rrandom/CodeMirror,wingify/CodeMirror,qiankun007/CodeMirror,kangkot/CodeMirror,thomasjm/CodeMirror,SidPresse/CodeMirror,rrandom/CodeMirror,Ermlab/CodeMirror,mizchi/CodeMirror,ejgallego/CodeMirror,kuangyeheng/CodeMirror,Aliccer/CodeMirror,Icenium/CodeMirror,ksanaforge/CodeMirror,jochenberger/CodeMirror,thomasjm/CodeMirror,bfrohs/CodeMirror,codio/CodeMirror,EasonYi/CodeMirror,abdelouahabb/CodeMirror,TechnicalPursuit/CodeMirror,shiren/CodeMirror,Jisuanke/CodeMirror,ashmind/CodeMirror,jessegrosjean/CodeMirror,amshali/CodeMirror,cintiamh/CodeMirror,qiankun007/CodeMirror,jkaplon/CodeMirror,michaelerobertsjr/CodeMirror,crazy4chrissi/CodeMirror,bfrohs/CodeMirror,manderson23/CodeMirror,AlanWasTaken/codemirror,crazy4chrissi/CodeMirror,sanyaade-iot/CodeMirror,ficristo/CodeMirror,NeZaMy/CodeMirror2,morrisonwudi/CodeMirror,Aliccer/CodeMirror,loopspace/CodeMirror,grzegorzmazur/CodeMirror,schanzer/CodeMirror,pinbe/CodeMirror,rasata/CodeMirror,cintiamh/CodeMirror,qweasd1/CodeMirror,jayaprabhakar/CodeMirror,ssxxue/CodeMirror,mizchi/CodeMirror,ZombieHippie/CodeMirror,amshali/CodeMirror,isdampe/CodeMirror,MarcelGerber/CodeMirror,belph/CodeMirror,sourcelair/CodeMirror,abdelouahabb/CodeMirror,Allenice/CodeMirror,pabloferz/CodeMirror,happibum/CodeMirror-main,dbarnett/CodeMirror,tpphu/CodeMirror,apatawari/CodeMirror,DustinH/CodeMirror,ThebingServices/CodeMirror,kolya-ay/CodeMirror,ThebingServices/CodeMirror,sgoo/CodeMirror,mtaran-google/CodeMirror,axter/CodeMirror,notepadqq/CodeMirror,melpon/CodeMirror,trumanliu/CodeMirror,buchslava/CodeMirror,nawroth/CodeMirror,kangkot/CodeMirror,ficristo/CodeMirror,angelozerr/CodeMirror,happibum/CodeMirror-main,Navaneethsen/CodeMirror,bluesh55/CodeMirror,mightyguava/CodeMirror,ksanaforge/CodeMirror,sanyaade-iot/CodeMirror,Dominator008/CodeMirror,amsul/CodeMirror,karthikeyansam/CodeMirror,loopspace/CodeMirror,ficristo/CodeMirror,codio/CodeMirror,antimatter15/CodeMirror,amsul/CodeMirror,belph/CodeMirror,davidpham87/CodeMirror,TDaglis/CodeMirror,amireh/codemirror,adobe/CodeMirror2,joshterrell805-historic/CodeMirror,r7kamura/CodeMirror,systay/CodeMirror,supriyantomaftuh/CodeMirror,namin/CodeMirror,increpare/CodeMirror,karthikeyansam/CodeMirror,hccampos/CodeMirror,notepadqq/CodeMirror,davidpham87/CodeMirror,gkoberger/CodeMirror,nawroth/CodeMirror,grzegorzmazur/CodeMirror,systay/CodeMirror,webida/CodeMirror,karthikeyansam/CodeMirror,morrisonwudi/CodeMirror,shiren/CodeMirror,Jisuanke/CodeMirror,kk9599/CodeMirror,anthonygego/CodeMirror,buchslava/CodeMirror,rasata/CodeMirror,flyskyko/CodeMirror,sgoo/CodeMirror,skylarkcob/CodeMirror,flyskyko/CodeMirror,thomasjm/CodeMirror,melpon/CodeMirror,kk9599/CodeMirror,hackmdio/CodeMirror,nightwing/CodeMirror,xeronith/CodeMirror,TechnicalPursuit/CodeMirror,trumanliu/CodeMirror,InternetGuru/CodeMirror,michaelerobertsjr/CodeMirror,MarcelGerber/CodeMirror,CartoDB/CodeMirror,ksanaforge/CodeMirror,qweasd1/CodeMirror,webida/CodeMirror,vincentwoo/CodeMirror,kangkot/CodeMirror,agendor/CodeMirror,GerHobbelt/CodeMirror2,flyskyko/CodeMirror,pjkui/CodeMirror,philuchansky/CodeMirror,shiren/CodeMirror,vanloswang/CodeMirror,explorigin/CodeMirror,bgrins/CodeMirror,bocharsky-bw/CodeMirror,fpco/codemirror,mizchi/CodeMirror,elisee/CodeMirror,philuchansky/CodeMirror,symbla/CodeMirror,matthewbauer/CodeMirror,dperetti/CodeMirror,camellhf/CodeMirror,webida/CodeMirror,sourcelair/CodeMirror,pjkui/CodeMirror,alur/CodeMirror,Navaneethsen/CodeMirror,KamranMackey/CodeMirror,wingify/CodeMirror,d0liver/CodeMirror,supriyantomaftuh/CodeMirror,r7kamura/CodeMirror,mihailik/CodeMirror,anthonygego/CodeMirror,ejgallego/CodeMirror,dbarnett/CodeMirror,djadmin/CodeMirror,skylarkcob/CodeMirror,morrisonwudi/CodeMirror,jessegrosjean/CodeMirror,DustinH/CodeMirror,kerabromsmu/CodeMirror,jhnesk/CodeMirror,d0liver/CodeMirror,xeronith/CodeMirror,cben/CodeMirror,explorigin/CodeMirror,axter/CodeMirror,pinbe/CodeMirror,philuchansky/CodeMirror,dudb/CodeMirror,dudb/CodeMirror,sourcelair/CodeMirror,bluesh55/CodeMirror,Dominator008/CodeMirror,belph/CodeMirror,jochenberger/CodeMirror,mightyguava/CodeMirror,GerHobbelt/CodeMirror2,sekcheong/CodeMirror,increpare/CodeMirror,dperetti/CodeMirror,TDaglis/CodeMirror,karevn/CodeMirror,agendor/CodeMirror,alur/CodeMirror,SidPresse/CodeMirror,bocharsky-bw/CodeMirror,namin/CodeMirror,trumanliu/CodeMirror,elisee/CodeMirror,cben/CodeMirror,INTELOGIE/CodeMirror,Jisuanke/CodeMirror,increpare/CodeMirror,NeZaMy/CodeMirror2,namin/CodeMirror,apatawari/CodeMirror,Allenice/CodeMirror,EasonYi/CodeMirror,sekcheong/CodeMirror,skylarkcob/CodeMirror,angelozerr/CodeMirror,TDaglis/CodeMirror,ThebingServices/CodeMirror,kevinushey/CodeMirror,fmoliveira/CodeMirror,matthewbauer/CodeMirror,rustemferreira/CodeMirror,vincentwoo/CodeMirror,hccampos/CodeMirror,systay/CodeMirror,mtaran-google/CodeMirror,bgrins/CodeMirror,Number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