certificate: Return signature scheme and parameters from issued_by() method

This also required some include restructuring (avoid including library.h
in headers) to avoid unresolvable circular dependencies.

src/libstrongswan/utils/debug.h

@@ -24,9 +24,9 @@
 typedef enum debug_t debug_t;
 typedef enum level_t level_t;
 
-#include <stdio.h>
-
+#include <utils/printf_hook/printf_hook.h>
 #include <utils/utils.h>
+#include <stdio.h>
 
 /**
  * Debug message group.