[commonlisp mode] Recognize character literal syntax
[commonlisp mode] Recognize character literal syntax

Closes #4401

SidPresse/CodeMirror,mtaran-google/CodeMirror,mtaran-google/CodeMirror,mtaran-google/CodeMirror,ficristo/CodeMirror,xeronith/CodeMirror,thomasjm/CodeMirror,schanzer/CodeMirror,jkaplon/CodeMirror,pabloferz/CodeMirror,thomasjm/CodeMirror,MarcelGerber/CodeMirror,dperetti/CodeMirror,kerabromsmu/CodeMirror,TDaglis/CodeMirror,dperetti/CodeMirror,crazy4chrissi/CodeMirror,grzegorzmazur/CodeMirror,pabloferz/CodeMirror,hackmdio/CodeMirror,kerabromsmu/CodeMirror,wingify/CodeMirror,jkaplon/CodeMirror,wingify/CodeMirror,hackmdio/CodeMirror,MarcelGerber/CodeMirror,dperetti/CodeMirror,nightwing/CodeMirror,TDaglis/CodeMirror,ejgallego/CodeMirror,pabloferz/CodeMirror,rrandom/CodeMirror,kerabromsmu/CodeMirror,codio/CodeMirror,codio/CodeMirror,jayaprabhakar/CodeMirror,xeronith/CodeMirror,namin/CodeMirror,jayaprabhakar/CodeMirror,rrandom/CodeMirror,SidPresse/CodeMirror,namin/CodeMirror,TDaglis/CodeMirror,notepadqq/CodeMirror,ejgallego/CodeMirror,hackmdio/CodeMirror,ficristo/CodeMirror,nightwing/CodeMirror,namin/CodeMirror,notepadqq/CodeMirror,schanzer/CodeMirror,nightwing/CodeMirror,notepadqq/CodeMirror,schanzer/CodeMirror,MarcelGerber/CodeMirror,ejgallego/CodeMirror,crazy4chrissi/CodeMirror,xeronith/CodeMirror,crazy4chrissi/CodeMirror,grzegorzmazur/CodeMirror,grzegorzmazur/CodeMirror,jayaprabhakar/CodeMirror,wingify/CodeMirror,SidPresse/CodeMirror,thomasjm/CodeMirror,jkaplon/CodeMirror,rrandom/CodeMirror,codio/CodeMirror,ficristo/CodeMirror