+PH/10 Tidied the code in a number of places where the st_size field of a stat()
+ result is used (not including appendfile, where other changes are about
+ to be made).
+
+PH/11 Upgraded appendfile so that quotas larger than 2G are now supported.
+ This involved changing a lot of size variables from int to off_t. It
+ should work with maildirs and everything.
+