Use #include <foo.h> instead of #include "foo.h" in most cases.

We rely on the include path to find many of these headers.  It
especially doesn't make sense to use #include "foo.h" for headers
in the top-level include directory.

lib/util/sig2str.c

@@ -31,8 +31,8 @@
 #include <signal.h>
 #include <unistd.h>
 
-#include "sudo_compat.h"
-#include "sudo_util.h"
+#include <sudo_compat.h>
+#include <sudo_util.h>
 
 #if !defined(HAVE_SIGABBREV_NP)
 # if defined(HAVE_DECL_SYS_SIGNAME) && HAVE_DECL_SYS_SIGNAME == 1