Add a script to tell whether a file can be perfectly parsed by spatch

spatch can let us know whether a file has parsed "perfectly" or
not.  The more perfect it parses, the likelier any semantic patches
are to apply.  I've used this script to identify problem areas in
our code.

scripts/coccinelle/try_parse.sh

+#!/bin/sh
+
+# Echo the name of every argument of this script that is not "perfect"
+# according to coccinelle's --parse-c.
+
+top="$(dirname "$0")/../.."
+
+for fn in "$@"; do
+
+    if spatch -macro_file_builtins "$top"/scripts/coccinelle/tor-coccinelle.h \
+              -I "$top" -I "$top"/src -I "$top"/ext --parse-c "$fn" \
+              2>/dev/null | grep "perfect = 1" > /dev/null; then
+        : # it's perfect
+    else
+        echo "$fn"
+    fi
+
+done