Add tests for krb5_sname_match()

(cherry picked from commit 83dae972736d823216c20dd559e30c7d41361289)

https://github.com/krb5/krb5/commit/be5d832b0b74ca3102cc916541e23ea4c9cb7a81
Author: Greg Hudson <ghudson@mit.edu>
Committer: Tom Yu <tlyu@mit.edu>
Commit: be5d832b0b74ca3102cc916541e23ea4c9cb7a81
Branch: krb5-1.14
 .gitignore                       |    1 +
 src/lib/krb5/krb/Makefile.in     |   11 +++-
 src/lib/krb5/krb/t_sname_match.c |  117 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 127 insertions(+), 2 deletions(-)