Support older versions of "prove"

Apparently, older versions of "prove" (couldn't identify the exact
version from the changelog) don't look into the t/ directory for tests
by default, so specify it explicitly.

src/Makefile.global.in

@@ -311,13 +311,13 @@ $(if $(filter $(PORTNAME),darwin),DYLD_LIBRARY_PATH,$(if $(filter $(PORTNAME),ai
 endef
 
 define prove_installcheck
-cd $(srcdir) && TESTDIR='$(CURDIR)' PATH="$(bindir):$$PATH" PGPORT='6$(DEF_PGPORT)' $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS)
+cd $(srcdir) && TESTDIR='$(CURDIR)' PATH="$(bindir):$$PATH" PGPORT='6$(DEF_PGPORT)' $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS) t/
 endef
 
 define prove_check
 $(MKDIR_P) tmp_check/log
 $(MAKE) -C $(top_builddir) DESTDIR=$(CURDIR)/tmp_check/install install >$(CURDIR)/tmp_check/log/install.log 2>&1
-cd $(srcdir) && TESTDIR='$(CURDIR)' PATH="$(CURDIR)/tmp_check/install$(bindir):$$PATH" $(call add_to_path,$(ld_library_path_var),$(CURDIR)/tmp_check/install$(libdir)) PGPORT='6$(DEF_PGPORT)' $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS)
+cd $(srcdir) && TESTDIR='$(CURDIR)' PATH="$(CURDIR)/tmp_check/install$(bindir):$$PATH" $(call add_to_path,$(ld_library_path_var),$(CURDIR)/tmp_check/install$(libdir)) PGPORT='6$(DEF_PGPORT)' $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS) t/
 endef
 
 # Installation.