Convert P images with transparency into RGBA
Convert P images with transparency into RGBA

Fixes #800

taedori81/wagtail,dresiu/wagtail,serzans/wagtail,nimasmi/wagtail,taedori81/wagtail,zerolab/wagtail,JoshBarr/wagtail,kurtw/wagtail,gasman/wagtail,takeflight/wagtail,darith27/wagtail,kurtw/wagtail,kaedroho/wagtail,chimeno/wagtail,rv816/wagtail,jorge-marques/wagtail,m-sanders/wagtail,takeshineshiro/wagtail,iho/wagtail,rsalmaso/wagtail,iansprice/wagtail,stevenewey/wagtail,darith27/wagtail,kurtw/wagtail,takeshineshiro/wagtail,rjsproxy/wagtail,janusnic/wagtail,serzans/wagtail,Pennebaker/wagtail,m-sanders/wagtail,kurtw/wagtail,kurtrwall/wagtail,bjesus/wagtail,mixxorz/wagtail,rv816/wagtail,KimGlazebrook/wagtail-experiment,jorge-marques/wagtail,mixxorz/wagtail,timorieber/wagtail,inonit/wagtail,nealtodd/wagtail,mixxorz/wagtail,JoshBarr/wagtail,wagtail/wagtail,nilnvoid/wagtail,mayapurmedia/wagtail,gogobook/wagtail,quru/wagtail,nimasmi/wagtail,Toshakins/wagtail,bjesus/wagtail,nrsimha/wagtail,FlipperPA/wagtail,nrsimha/wagtail,mjec/wagtail,hanpama/wagtail,takeshineshiro/wagtail,janusnic/wagtail,mephizzle/wagtail,Toshakins/wagtail,rjsproxy/wagtail,jnns/wagtail,jordij/wagtail,takeflight/wagtail,FlipperPA/wagtail,kaedroho/wagtail,Klaudit/wagtail,davecranwell/wagtail,chrxr/wagtail,WQuanfeng/wagtail,gogobook/wagtail,hanpama/wagtail,darith27/wagtail,mikedingjan/wagtail,KimGlazebrook/wagtail-experiment,nutztherookie/wagtail,chimeno/wagtail,mephizzle/wagtail,jorge-marques/wagtail,hamsterbacke23/wagtail,mayapurmedia/wagtail,chrxr/wagtail,nilnvoid/wagtail,rsalmaso/wagtail,taedori81/wagtail,KimGlazebrook/wagtail-experiment,mixxorz/wagtail,m-sanders/wagtail,inonit/wagtail,taedori81/wagtail,iansprice/wagtail,marctc/wagtail,gasman/wagtail,kaedroho/wagtail,thenewguy/wagtail,janusnic/wagtail,iansprice/wagtail,inonit/wagtail,dresiu/wagtail,nrsimha/wagtail,kaedroho/wagtail,mikedingjan/wagtail,nutztherookie/wagtail,iho/wagtail,tangentlabs/wagtail,nimasmi/wagtail,m-sanders/wagtail,Klaudit/wagtail,Tivix/wagtail,rv816/wagtail,serzans/wagtail,torchbox/wagtail,zerolab/wagtail,mikedingjan/wagtail,wagtail/wagtail,nealtodd/wagtail,dresiu/wagtail,iho/wagtail,taedori81/wagtail,mayapurmedia/wagtail,takeshineshiro/wagtail,timorieber/wagtail,Pennebaker/wagtail,dresiu/wagtail,thenewguy/wagtail,thenewguy/wagtail,rjsproxy/wagtail,Klaudit/wagtail,wagtail/wagtail,iansprice/wagtail,nutztherookie/wagtail,tangentlabs/wagtail,thenewguy/wagtail,hanpama/wagtail,stevenewey/wagtail,chimeno/wagtail,rv816/wagtail,nealtodd/wagtail,jnns/wagtail,serzans/wagtail,nutztherookie/wagtail,timorieber/wagtail,torchbox/wagtail,WQuanfeng/wagtail,darith27/wagtail,mephizzle/wagtail,kaedroho/wagtail,stevenewey/wagtail,tangentlabs/wagtail,hanpama/wagtail,bjesus/wagtail,jordij/wagtail,chimeno/wagtail,iho/wagtail,gasman/wagtail,Pennebaker/wagtail,davecranwell/wagtail,takeflight/wagtail,torchbox/wagtail,nimasmi/wagtail,thenewguy/wagtail,rsalmaso/wagtail,janusnic/wagtail,mikedingjan/wagtail,jorge-marques/wagtail,Klaudit/wagtail,Tivix/wagtail,hamsterbacke23/wagtail,nilnvoid/wagtail,kurtrwall/wagtail,inonit/wagtail,jnns/wagtail,benjaoming/wagtail,torchbox/wagtail,jorge-marques/wagtail,Toshakins/wagtail,mjec/wagtail,takeflight/wagtail,nilnvoid/wagtail,kurtrwall/wagtail,chrxr/wagtail,mjec/wagtail,rjsproxy/wagtail,chrxr/wagtail,dresiu/wagtail,gasman/wagtail,kurtrwall/wagtail,hamsterbacke23/wagtail,mephizzle/wagtail,gogobook/wagtail,jordij/wagtail,marctc/wagtail,jnns/wagtail,JoshBarr/wagtail,WQuanfeng/wagtail,jordij/wagtail,benjaoming/wagtail,gasman/wagtail,davecranwell/wagtail,marctc/wagtail,zerolab/wagtail,nealtodd/wagtail,chimeno/wagtail,benjaoming/wagtail,Pennebaker/wagtail,mixxorz/wagtail,timorieber/wagtail,Tivix/wagtail,marctc/wagtail,davecranwell/wagtail,mjec/wagtail,quru/wagtail,Toshakins/wagtail,benjaoming/wagtail,quru/wagtail,FlipperPA/wagtail,zerolab/wagtail,gogobook/wagtail,JoshBarr/wagtail,KimGlazebrook/wagtail-experiment,rsalmaso/wagtail,quru/wagtail,wagtail/wagtail,bjesus/wagtail,nrsimha/wagtail,Tivix/wagtail,rsalmaso/wagtail,wagtail/wagtail,zerolab/wagtail,tangentlabs/wagtail,hamsterbacke23/wagtail,stevenewey/wagtail,mayapurmedia/wagtail,FlipperPA/wagtail,WQuanfeng/wagtail