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.

plugins/group_file/plugin_test.c

@@ -32,7 +32,7 @@
 #include <string.h>
 #include <unistd.h>
 
-#include "sudo_plugin.h"
+#include <sudo_plugin.h>
 
 sudo_dso_public int main(int argc, char *argv[]);