RAR5 reader: fix invalid memory access in some files

RAR5 reader: fix invalid memory access in some files

RAR5 reader uses several variables to manage the window buffer during
extraction: the buffer itself (`window_buf`), the current size of the
window buffer (`window_size`), and a helper variable (`window_mask`)
that is used to constrain read and write offsets to the window buffer.

Some specially crafted files can force the unpacker to update the
`window_mask` variable to a value that is out of sync with current
buffer size. If the `window_mask` will be bigger than the actual buffer
size, then an invalid access operation can happen (SIGSEGV).

This commit ensures that if the `window_size` and `window_mask` will be
changed, the window buffer will be reallocated to the proper size, so no
invalid memory operation should be possible.

This commit contains a test file from OSSFuzz #30442.