Fix two omissions in stdint.h changes

Since we no longer prefix an "#include <stdint.h>" in the gssapi.h
preamble at build time, include it in gssapi.hin.

Update util/gss/kernel-lib/Makefile.in to account for gssapi_krb5.h
being in the source tree.
Admin doc corrections with `kdb5_util load`

Revised the example usage purpose statement for invoking `kdb5_util
load -update` to clarify that loading a second dump made via -ov
switch was no longer necessary since the -r13 format became the
default.  -b7 applied to versions prior to 1.2.2.