rar5: Fix Visual Studio compiler warnings (#2187)

rar5: Fix Visual Studio compiler warnings (#2187)

Turning window_mask into ssize_t and adjusting the signature of
circular_memcpy reduces the amount of required casts. Since window_mask
depends on value window_size, which is ssize_t, this change is safe.

Also turned extra_data_size into int64_t, which is a no-op on 64 bit
systems but prevents 32 bit systems from truncating these huge values in
archives. Since these systems most likely have large file support, this
could have meant truncation -- in theory.