dest_thy_const : term -> {Thy:string, Name:string, Ty:hol_type}
SYNOPSIS
Breaks apart a constant into name, theory, and type.
DESCRIBE
dest_thy_const is a term destructor for constants. If M is a
constant declared in theory Thy with name Name and type ty,
then dest_thy_const M returns {Thy, Name, Ty}, where Ty is an
instance of ty.