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.
diff --git a/runtime/syntax/testdir/input/sh_09.sh b/runtime/syntax/testdir/input/sh_09.sh
new file mode 100644
index 0000000..9888ade
--- /dev/null
+++ b/runtime/syntax/testdir/input/sh_09.sh
@@ -0,0 +1,19 @@
+#!/bin/sh
+# Test file for vim the check () subshells
+( cd ; $pwd ) | wc -c
+( cd $1 ; $pwd ) | wc -c
+( cd ${1} ; $pwd ) | wc -c
+( cd ; $pwd ) | wc -c
+( cd ${1:-.} ; $pwd ) | sed -e 's!$!/!' -e 's!//*$!/!'
+( cd ; $pwd ) | wc -c
+( cd ${1:+.} ; $pwd ) | wc -c
+( cd ; $pwd ) | wc -c
+( cd ${1:=.} ; $pwd ) | wc -c
+( cd ; $pwd ) | wc -c
+( cd ${1:?}  ; $pwd ) | wc -c
+( cd ; $pwd ) | wc -c
+( cd $HOME ; $pwd ) | wc -c
+( cd ${HOME} ; $pwd ) | wc -c
+( cd ${HOME} ) | wc -c
+((n=1+2))
+let n=1+2