are in kvm_uread():
- the setting of errno before checking it in the lseek() was lost.
- EOF handling was lost. kvm_uread() retried forever on EOF. EOF is
not really an error, but report it one as in rev.1.2.
- reporting of errno after a read error was lost.
Fixed style bugs in rev.1.3 and rev.1.12.
Not fixed: errno is not reported after lseek() failures.
ff6b6a564b