added a pre in withNewStackFrame (now withNewScope)
added a pre in withNewStackFrame (now withNewScope)

Also, some comments on typeclasses and SMTPat

FStarLang/FStar,YaccConstructor/FStar,msprotz/FStar,YaccConstructor/FStar,msprotz/FStar,msprotz/FStar,YaccConstructor/FStar,MallabaevAzamat/FStar,aa755/FStar,hoheinzollern/FStar,A-Manning/FStar,FStarLang/FStar,aa755/FStar,aa755/FStar,MallabaevAzamat/FStar,aa755/FStar,A-Manning/FStar,MallabaevAzamat/FStar,msprotz/FStar,YaccConstructor/FStar,hoheinzollern/FStar,MallabaevAzamat/FStar,hoheinzollern/FStar,FStarLang/FStar,A-Manning/FStar,hoheinzollern/FStar