various files - fix some alerts raised by lgtm code analysis

This patch fixes several issues reported by the lgtm code analysis tool:

https://lgtm.com/projects/g/asterisk/asterisk

Not all reported issues were addressed in this patch. This patch mostly fixes
confirmed reported errors, potential problematic code points, and a few other
"low hanging" warnings or recommendations found in core supported modules.
These include, but are not limited to the following:

* innapropriate stack allocation in loops
* buffer overflows
* variable declaration "hiding" another variable declaration
* comparisons results that are always the same
* ambiguously signed bit-field members
* missing header guards

Change-Id: Id4a881686605d26c94ab5409bc70fcc21efacc25

res/parking/parking_bridge_features.c

@@ -69,7 +69,7 @@ struct parked_subscription_datastore {
 struct parked_subscription_data {
 	struct transfer_channel_data *transfer_data;
 	char *parkee_uuid;
-	int hangup_after:1;
+	unsigned int hangup_after:1;
 	char parker_uuid[0];
 };
 

res/parking/res_parking.h

@@ -23,6 +23,9 @@
  * \author Jonathan Rose <jrose@digium.com>
  */
 
+#ifndef ASTERISK_RES_PARKING_H
+#define ASTERISK_RES_PARKING_H
+
 #include "asterisk/pbx.h"
 #include "asterisk/bridge.h"
 #include "asterisk/parking.h"
@@ -574,3 +577,5 @@ int load_parking_tests(void);
  * \return Nothing
  */
 void unload_parking_tests(void);
+
+#endif /* ASTERISK_RES_PARKING_H */