check mksh version, reported by joerg

Makefile

@@ -161,6 +161,11 @@ NO_ERROR=0
 	@if ! mksh -c 'echo $$KSH_VERSION' 2>&1 | fgrep 'MIRBSD' >/dev/null 2>&1; then \
 		echo "MirBSD ksh (mksh) needs to be installed."; \
 		exit 1; \
+	else \
+		if [ $$(mksh -c 'echo $$KSH_VERSION' |cut -d ' ' -f 3|sed "s#R##") -le 38 ]; then \
+			echo "MirBSD ksh is too old. R38 or higher needed."; \
+			exit 1; \
+		fi \
 	fi
 	@if test x"$$(umask 2>/dev/null | sed 's/00*22/OK/')" != x"OK"; then \
 		echo >&2 Error: you must build with umask 022, sorry.; \