Added libc.exit in SimProcedure.
Added libc.exit in SimProcedure.

tyb0807/angr,zhuyue1314/simuvex,tyb0807/angr,axt/angr,angr/simuvex,angr/angr,f-prettyland/angr,chubbymaggie/simuvex,tyb0807/angr,chubbymaggie/angr,schieb/angr,chubbymaggie/simuvex,angr/angr,iamahuman/angr,f-prettyland/angr,angr/angr,chubbymaggie/angr,iamahuman/angr,chubbymaggie/simuvex,axt/angr,iamahuman/angr,f-prettyland/angr,chubbymaggie/angr,schieb/angr,schieb/angr,axt/angr