common/util.h: dodgy non-__GNUC__ p_delete

I assume nobody have tried to compile Awesome with GNU uncompatible
compiler for ages and thus non-__GNUC__ p_delete version got
overlooked for quite some time.
First of all, a problem I see is that it assigns void** to a variable
of type void* and then dereferences the same void* variable.
None of the compilers I am aware of will let you go through this
without an error.
And second of all, lets have one portable p_delete.

Signed-off-by: Arvydas Sidorenko <asido4@gmail.com>
Signed-off-by: Uli Schlachter <psychon@znc.in>

common/util.h

@@ -80,31 +80,19 @@
         }                                            \
     } while (0)
 
-
-#ifdef __GNUC__
-
-#define p_delete(mem_pp)                           \
-    do {                                           \
-        typeof(**(mem_pp)) **__ptr = (mem_pp);     \
-        free(*__ptr);                              \
-        *__ptr = NULL;                             \
-    } while(0)
-
-#define likely(expr)    __builtin_expect(!!(expr), 1)
-#define unlikely(expr)  __builtin_expect((expr), 0)
-
-#else
-
 #define p_delete(mem_p)                              \
     do {                                             \
-        void *__ptr = (mem_p);                     \
+        void **__ptr = (void **) (mem_p);            \
         free(*__ptr);                                \
         *(void **)__ptr = NULL;                      \
     } while (0)
 
+#ifdef __GNUC__
+#define likely(expr)    __builtin_expect(!!(expr), 1)
+#define unlikely(expr)  __builtin_expect((expr), 0)
+#else
 #define likely(expr)    expr
 #define unlikely(expr)  expr
-
 #endif
 
 static inline void * __attribute__ ((malloc)) xmalloc(ssize_t size)