Add a ./configure flag "DIST_LANG" to select which langauge to include
in a distribution package.
diff --git a/configure.ac b/configure.ac
index 58c1bf3..c3b04e0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -20,6 +20,14 @@
AC_CONFIG_HEADERS([config.h])
AC_CONFIG_MACRO_DIR([m4])
+AC_ARG_VAR(DIST_LANG, [language to include in the distribution package (i.e., make dist)])
+case "$DIST_LANG" in
+ "") DIST_LANG=cpp ;;
+ all | cpp | java | python | javanano) ;;
+ *) AC_MSG_FAILURE([unknown language: $DIST_LANG]) ;;
+esac
+AC_SUBST(DIST_LANG)
+
# autoconf's default CXXFLAGS are usually "-g -O2". These aren't necessarily
# the best choice for libprotobuf.
AS_IF([test "x${ac_cv_env_CFLAGS_set}" = "x"],