Allow building with gcc-4.4

With this small patch, building succeeds with Debian's current gcc-snapshot,
gcc (Debian 20090107-1) 4.4.0 20090107 (experimental) [trunk revision 143170]

That build shows no regressions in the test suite.  The patch does not
break building, or show test suite regressions, with gcc-4.3.

That new gcc version still emits a pile of new and arguably bogus warnings
 "dereferencing pointer '<anonymous>' does break strict-aliasing rules" for
   elaborate.cc:3422
   StringHeap.h:31
   vvp/vvp_net.h:687  (really vvp/vvp_net.h:825)

t-dll-api.cc

@@ -22,6 +22,7 @@
 # include  "t-dll.h"
 # include  "discipline.h"
 # include  <stdlib.h>
+# include  <stdio.h>
 # include  <string.h>
 #ifdef HAVE_MALLOC_H
 # include  <malloc.h>