tnc-ifmap: Remove prototypical IF-MAP plugin

This was primarily used in our labs to visualize some TNC aspects but
the third-party daemon and frontend we used have not seen any development
in a decade.  There never was any industry interest in this protocol
anyway, so just remove it.

src/libcharon/Makefile.am

@@ -481,13 +481,6 @@ if MONOLITHIC
 endif
 endif
 
-if USE_TNC_IFMAP
-  SUBDIRS += plugins/tnc_ifmap
-if MONOLITHIC
-  libcharon_la_LIBADD += plugins/tnc_ifmap/libstrongswan-tnc-ifmap.la
-endif
-endif
-
 if USE_TNC_PDP
   SUBDIRS += plugins/tnc_pdp
 if MONOLITHIC