Remove malloc.h support and for C++ files use <c...> include files.

The functions (malloc, free, etc.) that used to be provided in
malloc.h are now provided in cstdlib for C++ files and stdlib.h for
C files. Since we require a C99 compliant compiler it makes sense
that malloc.h is no longer needed.

This patch also modifies all the C++ files to use the <c...>
version of the standard C header files (e.g. <cstdlib> vs
<stdlib.h>). Some of the files used the C++ version and others did
not. There are still a few other header changes that could be done,
but this takes care of much of it.

(Cherry-picked from 1993bf6f69)

StringHeap.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002-2009 Stephen Williams ([email protected])
+ * Copyright (c) 2002-2010 Stephen Williams ([email protected])
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -18,12 +18,9 @@
  */
 
 # include  "StringHeap.h"
-#ifdef HAVE_MALLOC_H
-# include  <malloc.h>
-#endif
-# include  <stdlib.h>
-# include  <string.h>
-# include  <assert.h>
+# include  <cstdlib>
+# include  <cstring>
+# include  <cassert>
 
 #ifdef CHECK_WITH_VALGRIND
 static char **string_pool = NULL;