src/basic: rename audit.[ch] → audit-util.[ch] and capability.[ch] → capability-util.[ch]

The files are named too generically, so that they might conflict with
the upstream project headers. Hence, let's add a "-util" suffix, to
clarify that this are just our utility headers and not any official
upstream headers.

src/basic/audit-util.c

@@ -22,7 +22,7 @@
 #include <errno.h>
 #include <stdio.h>
 
-#include "audit.h"
+#include "audit-util.h"
 #include "fd-util.h"
 #include "fileio.h"
 #include "macro.h"

src/basic/capability-util.c

@@ -26,7 +26,7 @@
 #include <sys/prctl.h>
 #include <unistd.h>
 
-#include "capability.h"
+#include "capability-util.h"
 #include "fileio.h"
 #include "log.h"
 #include "macro.h"