Add 'read-only principal' flag

Reserve the high-order 16 bits of dlgtype for flags.
Add DLGFLAG_READONLY_PRINC.  When specified, the get tickets dialog
does not allow the user to change the principal.

Signed-off-by: Kevin Wasserman <kevin.wasserman@painless-security.com>

https://github.com/krb5/krb5/commit/88f425a7169a1f1d38b89d80a167f58e8ce475e8
Author: Kevin Wasserman <kevin.wasserman@painless-security.com>
Committer: Ben Kaduk <kaduk@mit.edu>
Commit: 88f425a7169a1f1d38b89d80a167f58e8ce475e8
Branch: master
 src/windows/include/leashwin.h |    2 ++
 src/windows/leashdll/lsh_pwd.c |   36 ++++++++++++++++++------------------
 2 files changed, 20 insertions(+), 18 deletions(-)