char *
FooFileChunk(const char *filename, char *buf, off_t offset, off_t length)
Which only hashes part of a file.
Implement FooFile() in terms of this function.
Submitted by: roam
and SHA-1 when OBJFORMAT is not ELF. Add a warning to the man page
about how SHA-1 uses bswapl, which will trap on 80386es (and the kernel
should, but doesn't currently, emulate).