Add Kerberos specific GSS-API Extensions

Adds most of the Kerberos specific GSS-API extension methods.  These
methods are useful when migrating from the Kerberos API to GSS-API or
when needing Kerberos specific functionality that is not exposed in
GSS-API.

Signed-off-by: Jordan Borean <[email protected]>
[[email protected]: style and grammar things]

Author: jborean93

Diff for: README.txt

@@ -165,6 +165,8 @@ In addition to RFC 2743/2744, Python-GSSAPI also has support for:
 
 * GGF Extensions
 
+* Kerberos specific extensions
+
 The Team
 ========
 

Diff for: ci/lib-setup.sh

@@ -12,6 +12,8 @@ setup::debian::install() {
     else
         apt-get -y install krb5-{user,kdc,admin-server,multidev} libkrb5-dev \
                 gss-ntlmssp
+
+        export GSSAPI_KRB5_MAIN_LIB="/usr/lib/x86_64-linux-gnu/libkrb5.so"
     fi
 
     apt-get -y install gcc virtualenv python3-{virtualenv,dev} cython3
@@ -46,6 +48,7 @@ setup::fedora::install() {
 setup::rh::install() {
     setup::rh::yuminst krb5-{devel,libs,server,workstation} \
                        which gcc findutils gssntlmssp
+    export GSSAPI_KRB5_MAIN_LIB="/usr/lib64/libkrb5.so"
 
     if [ -f /etc/fedora-release ]; then
         setup::fedora::install

Diff for: docs/source/gssapi.raw.rst

@@ -173,6 +173,13 @@ Acquiring Credentials With a Password Extensions
     :members:
     :undoc-members:
 
+Kerberos Specific Extensions
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. automodule:: gssapi.raw.ext_krb5
+    :members:
+    :undoc-members:
+
 Other Extensions
 ~~~~~~~~~~~~~~~~
 

Diff for: gssapi/raw/__init__.py

@@ -125,6 +125,12 @@
 except ImportError:
     pass
 
+# optional KRB5 specific extension support
+try:
+    from gssapi.raw.ext_krb5 import *  # noqa
+except ImportError:
+    pass
+
 # optional RFC 6680 support
 try:
     from gssapi.raw.ext_rfc6680 import *  # noqa

Diff for: gssapi/raw/ext_krb5.pxd

@@ -0,0 +1,2 @@
+cdef class Krb5LucidContext:
+    cdef void *raw_ctx