internal: delete VIR_STEAL_PTR

Delete the macro to prevent its usage in new code.

The GLib version should be used instead:
    p = g_steal_pointer(&ptr);

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

src/internal.h

@@ -213,18 +213,6 @@
         (a) = (a) ^ (b); \
     } while (0)
 
-/**
- * VIR_STEAL_PTR:
- *
- * Steals pointer passed as second argument into the first argument. Second
- * argument must not have side effects.
- */
-#define VIR_STEAL_PTR(a, b) \
-    do { \
-        (a) = (b); \
-        (b) = NULL; \
-    } while (0)
-
 /**
  * virCheckFlags:
  * @supported: an OR'ed set of supported flags