Add error test case for unterminated strings in the config file

test/120_parser_unterminated_string.cfg

@@ -0,0 +1,24 @@
+BOX testbox1
+
+escaped   "aaa\"bbb\\\"ccc#"   # the string aaa"bbb\"ccc#
+errored  "aaa\\"bbb"           # unterminated!
+
+sample
+    #
+    #  regular comments used in Perl, Shell scripts, etc.
+    #
+ends
+
+shapes {
+     w ("#")
+}
+
+elastic (
+	w
+)
+
+padding {
+	left 1
+}
+
+END testbox1

test/120_parser_unterminated_string.txt

@@ -0,0 +1,11 @@
+:ARGS
+-f 120_parser_unterminated_string.cfg
+:INPUT
+foo
+:OUTPUT-FILTER
+:EXPECTED-ERROR 1
+boxes: 120_parser_unterminated_string.cfg: line 4: Unterminated String -- "           # unterminated!
+boxes: 120_parser_unterminated_string.cfg: line 4: syntax error
+boxes: 120_parser_unterminated_string.cfg: line 4: skipping to next design
+boxes: 120_parser_unterminated_string.cfg: line 25: no valid designs found
+:EOF