tnccs-11: Remove legacy TNCCS-1.1 implementation

There is no reason to keep this around anymore (has been superseded by
TNCCS-2.0 a long time ago).  Removed the corresponding test scenarios.

Since this is the last user of libxml, also removed those references.

conf/Makefile.am

@@ -92,7 +92,6 @@ plugins = \
 	plugins/tnc-imc.opt \
 	plugins/tnc-imv.opt \
 	plugins/tnc-pdp.opt \
-	plugins/tnccs-11.opt \
 	plugins/tnccs-20.opt \
 	plugins/tpm.opt \
 	plugins/unbound.opt \

conf/plugins/tnccs-11.opt

@@ -1,2 +0,0 @@
-charon.plugins.tnccs-11.max_message_size = 45000
-	Maximum size of a PA-TNC message (XML & Base64 encoding).