d: add an example

* examples/d/calc.test, examples/d/calc.y, examples/d/local.mk:

examples/d/local.mk

@@ -0,0 +1,35 @@
+## Copyright (C) 2018 Free Software Foundation, Inc.
+##
+## This program is free software: you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+##
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+ddir = $(docdir)/%D%
+
+## ------ ##
+## Calc.  ##
+## ------ ##
+
+if ENABLE_D
+  check_SCRIPTS += %D%/calc
+  TESTS += %D%/calc.test
+endif
+
+%D%/calc.d: %D%/calc.y $(BISON_IN) $(dist_pkgdata_DATA)
+	$(AM_V_GEN)$(MKDIR_P) %D%
+	$(AM_V_at)$(BISON) $< -o $@
+
+%D%/calc: %D%/calc.d
+	$(AM_V_GEN) $(DC) $(DCFLAGS) -of$@ $<
+
+dist_d_DATA = %D%/calc.y
+CLEANFILES += %D%/calc %D%/Calc.d