KRB5: Enable MIT KRB5 by default

Set WITH_MITKRB5=yes as the default.

Rebuild all USES=gssapi ports is recommended.

A clean buildworld is required.

Relnotes:	yes

share/mk/src.opts.mk

@@ -143,6 +143,7 @@ __DEFAULT_YES_OPTIONS = \
     MAIL \
     MAILWRAPPER \
     MAKE \
+    MITKRB5 \
     MLX5TOOL \
     NETCAT \
     NETGRAPH \
@@ -211,7 +212,6 @@ __DEFAULT_NO_OPTIONS = \
     LOADER_VERIEXEC_PASS_MANIFEST \
     LLVM_FULL_DEBUGINFO \
     MALLOC_PRODUCTION \
-    MITKRB5 \
     OFED_EXTRA \
     OPENLDAP \
     REPRODUCIBLE_BUILD \