Fixups for env_copy with large files

wsize was being truncated to 32bits on Windows.
Only try to write 1GB at a time on Windows64;
larger writes fail with ERROR_WORKING_SET_QUOTA.

libraries/liblmdb/mdb.c

@@ -1271,7 +1271,7 @@ typedef struct MDB_ntxn {
 #endif
 
 	/** max bytes to write in one call */
-#define MAX_WRITE		(0x80000000U >> (sizeof(ssize_t) == 4))
+#define MAX_WRITE		(0x40000000U >> (sizeof(ssize_t) == 4))
 
 	/** Check \b txn and \b dbi arguments to a function */
 #define TXN_DBI_EXIST(txn, dbi, validity) \
@@ -9157,7 +9157,7 @@ mdb_env_copyfd0(MDB_env *env, HANDLE fd)
 	MDB_txn *txn = NULL;
 	mdb_mutexref_t wmutex = NULL;
 	int rc;
-	size_t wsize;
+	size_t wsize, w3;
 	char *ptr;
 #ifdef _WIN32
 	DWORD len, w2;
@@ -9216,15 +9216,15 @@ mdb_env_copyfd0(MDB_env *env, HANDLE fd)
 	if (rc)
 		goto leave;
 
-	w2 = txn->mt_next_pgno * env->me_psize;
+	w3 = txn->mt_next_pgno * env->me_psize;
 	{
 		size_t fsize = 0;
 		if ((rc = mdb_fsize(env->me_fd, &fsize)))
 			goto leave;
-		if (w2 > fsize)
-			w2 = fsize;
+		if (w3 > fsize)
+			w3 = fsize;
 	}
-	wsize = w2 - wsize;
+	wsize = w3 - wsize;
 	while (wsize > 0) {
 		if (wsize > MAX_WRITE)
 			w2 = MAX_WRITE;