a logic library; fix in make mathematical

examples/logic/TheoryEng.gf

@@ -0,0 +1,10 @@
+--# -path=.:mathematical:present:resource-1.0/api:prelude
+
+concrete TheoryEng of Theory = TheoryI with
+  (LexTheory = LexTheoryEng), 
+  (Grammar = GrammarEng), 
+  (Symbolic = SymbolicEng), 
+  (Symbol = SymbolEng), 
+  (Combinators = CombinatorsEng), 
+  (Constructors = ConstructorsEng), 
+  ;