Avoid unneeded additions while building object table.
Avoid unneeded additions while building object table.

Tracking @string_size, @int_size and @misc_size is only useful to compute the
byte position of the offset table, but this can actually be done just before
generating it by waiting to see how big the object table is. Avoiding the sums
improves performance on my test set by about 7%.

ckruse/CFPropertyList