configure: remove unneeded libtar

(cherry picked from commit 53ec4c4d)
Signed-off-by: Thomas Guillem <thomas@gllm.fr>

configure.ac

@@ -3935,14 +3935,6 @@ AS_IF([test "${enable_skins2}" != "no"], [
 ])
 AM_CONDITIONAL(BUILD_SKINS, [test "${enable_skins2}" = "yes"])
 
-AC_ARG_ENABLE(libtar,
-  [  --enable-libtar         libtar support for skins2 (default auto)])
-AS_IF([test "${enable_skins2}" = "yes" && test "${enable_libtar}" != "no"], [
-  AC_CHECK_HEADERS(libtar.h, [
-    VLC_ADD_LIBS([skins2],[-ltar])
-  ])
-])
-
 dnl
 dnl  MacOS X gui module
 dnl