Fix #alias_method for singleton classes
Fix #alias_method for singleton classes

Ported stuff from the #define_method impl. as per @adambeynon’s advice.
gausie/opal,kachick/opal,opal/opal,fazibear/opal,Mogztter/opal,Ajedi32/opal,castwide/opal,iliabylich/opal,gausie/opal,iliabylich/opal,jgaskins/opal,jannishuebl/opal,catprintlabs/opal,kachick/opal,c42engineering/opal,c42engineering/opal,c42engineering/opal,suyesh/opal,kachick/opal,kachick/opal,Ajedi32/opal,wied03/opal,bbatsov/opal,suyesh/opal,jannishuebl/opal,wied03/opal,gausie/opal,Mogztter/opal,Mogztter/opal,jannishuebl/opal,Flikofbluelight747/opal,Flikofbluelight747/opal,catprintlabs/opal,castwide/opal,merongivian/opal,gabrielrios/opal,Flikofbluelight747/opal,bbatsov/opal,gabrielrios/opal,iliabylich/opal,opal/opal,gabrielrios/opal,merongivian/opal,castwide/opal,Ajedi32/opal,fazibear/opal,catprintlabs/opal,Mogztter/opal,wied03/opal,suyesh/opal,opal/opal,jgaskins/opal,jgaskins/opal,bbatsov/opal,fazibear/opal,merongivian/opal,opal/opal