Fix Windows build errors in valgrind.h

valgrind.h is a verbatim copy taken from Valgrind project. Previously
that file had local changes that got dropped by last update. To avoid
regressing again, do not edit valgrind.h anymore and instead add a
gvalgrind.h wrapper that gets included instead.

This fix 2 errors:
- uintptr_t is not defined when including valgrind.h on mingw.
- MSVC compiler is not supported on amd64-Win64 platform.

gobject/gclosure.c

@@ -22,7 +22,7 @@
 
 #include "config.h"
 
-#include "../glib/valgrind.h"
+#include "../glib/gvalgrind.h"
 #include <string.h>
 
 #include <ffi.h>
@@ -200,6 +200,7 @@ g_closure_new_simple (guint           sizeof_closure,
 
   private_size = sizeof (GRealClosure) - sizeof (GClosure);
 
+#ifdef ENABLE_VALGRIND
   /* See comments in gtype.c about what's going on here... */
   if (RUNNING_ON_VALGRIND)
     {
@@ -213,6 +214,7 @@ g_closure_new_simple (guint           sizeof_closure,
       VALGRIND_MALLOCLIKE_BLOCK (allocated + sizeof (gpointer), private_size - sizeof (gpointer), 0, TRUE);
     }
   else
+#endif
     allocated = g_malloc0 (private_size + sizeof_closure);
 
   closure = (GClosure *) (allocated + private_size);
@@ -613,6 +615,7 @@ g_closure_unref (GClosure *closure)
       closure_invoke_notifiers (closure, FNOTIFY);
       g_free (closure->notifiers);
 
+#ifdef ENABLE_VALGRIND
       /* See comments in gtype.c about what's going on here... */
       if (RUNNING_ON_VALGRIND)
         {
@@ -627,6 +630,7 @@ g_closure_unref (GClosure *closure)
           VALGRIND_FREELIKE_BLOCK (closure, 0);
         }
       else
+#endif
         g_free (G_REAL_CLOSURE (closure));
     }
 }