coccinelle: add script to generate flags test

This patch adds a script which can be used to generate a test
on coherence of flag usage.

By adding comment in the code, it is possible to declare that we
link a flag in a structure to a specific family of constant:

For example:
	/* coccinelle: Packet:flowflags:FLOW_PKT_ */
will trigger the generation on a test which verifies that the
flowflags field in Packet structure is only used with constant
starting by FLOW_PKT_.

qa/coccinelle/struct-flags.py

@@ -0,0 +1,55 @@
+#!/usr/bin/env python
+import re
+from os import listdir
+
+SRC_DIR="../../src/"
+
+class Structure:
+    def __init__(self, string):
+        (self.struct, self.flags, self.values) = string.split(":")
+
+cmd = "grep -h coccinelle ../../src/*[ch] | sed -e 's/.*coccinelle: \(.*\) \*\//\1/'"
+
+struct_list = []
+
+dirList = listdir(SRC_DIR)
+for fname in dirList:
+    if re.search("\.[ch]$", fname):
+        for line in open(SRC_DIR + fname):
+            if "coccinelle:" in line:
+                m = re.search("coccinelle: (.*) \*\/", line)
+                struct = Structure(m.group(1))
+                struct_list.append(struct)
+
+header = "@flags@"
+body = []
+
+i = 0
+for struct in struct_list:
+    header += """
+%s *struct%d;
+identifier struct_flags%d =~ "^(?!%s).+";""" % ( struct.struct, i, i, struct.values)
+
+    body.append("""
+struct%d->%s@p1 |= struct_flags%d
+|
+struct%d->%s@p1 & struct_flags%d
+|
+struct%d->%s@p1 &= ~struct_flags%d
+""" % (i, struct.flags, i, i, struct.flags, i, i, struct.flags, i))
+
+    i+=1
+
+print header
+print "position p1;"
+print "@@"
+print ""
+print "(" + "|".join(body) + ")"
+print ""
+print """@script:python@
+p1 << flags.p1;
+@@
+
+print "Invalid usage of flags field at %s:%s, flags value is incorrect (wrong family)." % (p1[0].file, p1[0].line)
+import sys
+sys.exit(1)"""