Make sure that the Why3 library is visible from the plugin, since it references WhyType.

Makefile.in

@@ -795,12 +795,12 @@ src/coq-tactic/why3tac.ml: src/coq-tactic/why3tac.ml4
 
 src/coq-tactic/.why3-vo-byte: lib/coq-tactic/Why3.v lib/coq-tactic/why3tac.cma
 	$(if $(QUIET),@echo 'Coqc     $<' &&) \
-	    WHY3CONFIG="" $(COQC) -byte -R lib/coq-tactic Why3 $< && \
+	    WHY3CONFIG="" $(COQC) -byte -R lib/coq-tactic Why3 -R lib/coq Why3 $< && \
 	    touch src/coq-tactic/.why3-vo-byte
 
 src/coq-tactic/.why3-vo-opt: lib/coq-tactic/Why3.v lib/coq-tactic/why3tac.cmxs
 	$(if $(QUIET),@echo 'Coqc     $<' &&) \
-	    WHY3CONFIG="" $(COQC) -opt -R lib/coq-tactic Why3 $< && \
+	    WHY3CONFIG="" $(COQC) -opt -R lib/coq-tactic Why3 -R lib/coq Why3 $< && \
 	    touch src/coq-tactic/.why3-vo-opt
 
 # depend and clean targets
@@ -1432,10 +1432,10 @@ test-session.opt: examples/use_api/create_session.ml lib/why3/why3.cmxa
 	@rm -f test-session.opt why3session.xml why3shapes why3shapes.gz
 
 test-coq-tactic.byte: src/coq-tactic/.why3-vo-byte
-	$(COQC) -byte -R lib/coq-tactic Why3 bench/coq-tactic/test.v
+	$(COQC) -byte -R lib/coq-tactic Why3 -R lib/coq Why3 bench/coq-tactic/test.v
 
 test-coq-tactic.opt: src/coq-tactic/.why3-vo-opt
-	$(COQC) -opt -R lib/coq-tactic Why3 bench/coq-tactic/test.v
+	$(COQC) -opt -R lib/coq-tactic Why3 -R lib/coq Why3 bench/coq-tactic/test.v
 
 #only test the compilation of runstrat
 test-runstrat.byte: lib/why3/why3.cma lib/why3/META

lib/coq-tactic/Why3.v

+Require Import ZArith Reals Why3.BuiltIn.
+
 Declare ML Module "why3tac".