Issue #656:  Fix CVE-2016-1541, VU#862384

When reading OS X metadata entries in Zip archives that were stored
without compression, libarchive would use the uncompressed entry size
to allocate a buffer but would use the compressed entry size to limit
the amount of data copied into that buffer.  Since the compressed
and uncompressed sizes are provided by data in the archive itself,
an attacker could manipulate these values to write data beyond
the end of the allocated buffer.

This fix provides three new checks to guard against such
manipulation and to make libarchive generally more robust when
handling this type of entry:
 1. If an OS X metadata entry is stored without compression,
    abort the entire archive if the compressed and uncompressed
    data sizes do not match.
 2. When sanity-checking the size of an OS X metadata entry,
    abort this entry if either the compressed or uncompressed
    size is larger than 4MB.
 3. When copying data into the allocated buffer, check the copy
    size against both the compressed entry size and uncompressed
    entry size.
fake_crc32(unsigned long crc, const void *buff, size_t len)
{
	(void)crc; /* UNUSED */
	(void)buff; /* UNUSED */
	(void)len; /* UNUSED */
	return 0;
}

fake_crc32(unsigned long crc, const void *buff, size_t len)
{
	(void)crc; /* UNUSED */
	(void)buff; /* UNUSED */
	(void)len; /* UNUSED */
	return 0;
}
