patch 9.0.1647: insufficient testing for syntax plugins

Problem:    Insufficient testing for syntax plugins.
Solution:   Add shell file examples. (Charles Campbell)  Create a messages
            file for easier debugging and reporting the test results.

runtime/syntax/testdir/input/sh_02.sh

@@ -0,0 +1,30 @@
+#! /bin/ksh
+# sh2
+#  Jul 28, 2018: introduced shCommandSubBQ, which is *not* included in a shSubCommandList (so its not recursive)
+ccc=`echo "test"`
+	ccc=`echo "test"`
+
+# comment
+case $VAR in
+# comment
+	x|y|z) echo xyz ;;
+# comment
+	a|b|c) echo abc ;;
+# comment
+esac
+
+# Jul 26, 2018: why isn't `..` being terminated properly?
+# comment
+case "$aaa" in
+# comment
+  	bbb)  ccc=`echo $ddd|cut -b4-`
+	echo "test"
+# comment
+	;;
+# comment
+	esac
+# comment
+
+echo   $VAR abc
+export $VAR abc
+set    $VAR abc