how `crc' is actually defined.
- Remove an unnecessary `extern' variable declaration.
Data type corrections:
- Define a variable which contains a file byte offset value as type
off_t as required by the `crc' function.
- Change the type of a variable carrying a CRC checksum from `u_long'
to `uint32_t'.
- Substitute the wrong `extern' variable declaration of `crc_total'
by putting a correct one in the shared header extern.h.
`crc_total' is defined as an `uint32_t', thus fixing
incorrect mtree checksums on big-endian LP64 machines.
The way is now open to schg and sappnd key files and directories in
our tree. There are recommendations in bin/15229.
PR: bin/15229
Reviewed by: imp, brian
