Change MBR_read() and MBR_write() to return -1 on error and set

errno = EIO for short reads.  This makes it easier to check for
read and write errors.  Much patient tutoring by weingart@, deraadt@,
and cloder@.

Correctly use ssize_t to store read(2) and write(2) return values.

No functional change, since MBR_read() and MBR_write() return values
aren't currently checked.

OK deraadt@

0 files changed, 0 insertions, 0 deletions