Check for gssapi libraries and header files.

+# Based on gssapi.m4 by Brendan Cully <brendan@kublai.com> 20010529
+
+dnl MU_CHECK_GSSAPI(PREFIX)
+dnl Search for a GSSAPI implementation in the standard locations plus PREFIX,
+dnl if it is set and not "yes".
+dnl Defines GSSAPI_CFLAGS and GSSAPI_LIBS if found.
+dnl Defines GSSAPI_IMPL to "Heimdal", "MIT", or "OldMIT", or "none" if not found
+AC_DEFUN(MU_CHECK_GSSAPI,
+[
+ if test "x$mu_cv_lib_gssapi_libs" = x; then
+  cache=""
+  GSSAPI_PREFIX=[$1]
+  GSSAPI_IMPL="none"
+  # First try krb5-config
+  if test "$GSSAPI_PREFIX" != "yes"; then
+    krb5_path="$GSSAPI_PREFIX/bin"
+  else
+    krb5_path="$PATH"
+  fi
+  AC_PATH_PROG(KRB5CFGPATH, krb5-config, none, $krb5_path)
+  if test "$KRB5CFGPATH" != "none"; then
+    GSSAPI_CFLAGS="$CPPFLAGS `$KRB5CFGPATH --cflags gssapi`"
+    GSSAPI_LIBS="$MUTTLIBS `$KRB5CFGPATH --libs gssapi`"
+    GSSAPI_IMPL="Heimdal"
+  else
+    ## OK, try the old code
+    saved_CPPFLAGS="$CPPFLAGS"
+    saved_LDFLAGS="$LDFLAGS"
+    saved_LIBS="$LIBS"
+    if test "$GSSAPI_PREFIX" != "yes"; then
+      GSSAPI_CFLAGS="-I$GSSAPI_PREFIX/include"
+      GSSAPI_LDFLAGS="-L$GSSAPI_PREFIX/lib"
+      CPPFLAGS="$CPPFLAGS $GSSAPI_CFLAGS"
+      LDFLAGS="$LDFLAGS $GSSAPI_LDFLAGS"
+    fi
+
+    ## Check for new MIT kerberos V support
+    AC_CHECK_LIB(gssapi_krb5, gss_init_sec_context,
+      [GSSAPI_IMPL="MIT",
+       GSSAPI_LIBS="$GSSAPI_LDFLAGS -lgssapi_krb5 -lkrb5 -lk5crypto -lcom_err"]
+       ,, -lkrb5 -lk5crypto -lcom_err)
+
+    ## Heimdal kerberos V support
+    if test "$GSSAPI_IMPL" = "none"; then
+      AC_CHECK_LIB(gssapi, gss_init_sec_context,
+        [GSSAPI_IMPL="Heimdal"
+         GSSAPI_LIBS="$GSSAPI_LDFLAGS -lgssapi -lkrb5 -ldes -lasn1 -lroken"
+         GSSAPI_LIBS="$GSSAPI_LIBS -lcrypt -lcom_err"]
+         ,, -lkrb5 -ldes -lasn1 -lroken -lcrypt -lcom_err)
+    fi
+
+    ## Old MIT Kerberos V
+    ## Note: older krb5 distributions use -lcrypto instead of
+    ## -lk5crypto, which collides with OpenSSL.  One way of dealing
+    ## with that is to extract all objects from krb5's libcrypto
+    ## and from openssl's libcrypto into the same directory, then
+    ## to create a new libcrypto from these.
+    if test "$GSSAPI_IMPL" = "none"; then
+      AC_CHECK_LIB(gssapi_krb5, g_order_init,
+        [GSSAPI_IMPL="OldMIT",
+        GSSAPI_LIBS="$GSSAPI_LDFLAGS -lgssapi_krb5 -lkrb5 -lcrypto -lcom_err"]
+        ,, -lkrb5 -lcrypto -lcom_err)
+    fi
+  fi
+
+  mu_cv_lib_gssapi_cflags="$GSSAPI_CFLAGS"
+  mu_cv_lib_gssapi_libs="$GSSAPI_LIBS"
+  mu_cv_lib_gssapi_impl="$GSSAPI_IMPL"
+
+  LDFLAGS="$saved_LDFLAGS"
+  LIBS="$saved_LIBS"
+ else
+  cached=" (cached) "
+  GSSAPI_CFLAGS="$mu_cv_lib_gssapi_cflags"
+  GSSAPI_LIBS="$mu_cv_lib_gssapi_libs"
+  GSSAPI_IMPL="$mu_cv_lib_gssapi_impl"
+ fi
+ AC_MSG_CHECKING(GSSAPI implementation)
+ AC_MSG_RESULT(${cached}$GSSAPI_IMPL)
+])
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