misc: Introduce a more neutral configure option for CTRL/VTY

We started with only testing the VTY but now test VTY and CTRL
interface with this python framework and might even extend this
to SMPP. So add and "--enable-external-tests" directive which
enables the external interface tests.
diff --git a/openbsc/configure.ac b/openbsc/configure.ac
index 7c1803c..0777c0d 100644
--- a/openbsc/configure.ac
+++ b/openbsc/configure.ac
@@ -138,18 +138,23 @@
 
 AC_ARG_ENABLE([vty_tests],
 		AC_HELP_STRING([--enable-vty-tests],
-				[Include the VTY tests in make check [default=no]]),
-		[enable_vty_tests="$enableval"],[enable_vty_tests="no"])
-if test "x$enable_vty_tests" = "xyes" ; then
+				[Include the VTY/CTRL tests in make check (deprecated)
+				[default=no]]),
+		[enable_ext_tests="$enableval"],[enable_ext_tests="no"])
+AC_ARG_ENABLE([ext_tests],
+		AC_HELP_STRING([--enable-external-tests],
+				[Include the VTY/CTRL tests in make check [default=no]]),
+		[enable_ext_tests="$enableval"],[enable_ext_tests="no"])
+if test "x$enable_ext_tests" = "xyes" ; then
 	AM_PATH_PYTHON
-	AC_CHECK_PROG(OSMOTESTVTY_CHECK,osmotestvty.py,yes)
-	 if test "x$OSMOTESTVTY_CHECK" != "xyes" ; then
-		AC_MSG_ERROR([Please install osmocom-python to run the vty tests.])
+	AC_CHECK_PROG(OSMOTESTEXT_CHECK,osmotestvty.py,yes)
+	 if test "x$OSMOTESTEXT_CHECK" != "xyes" ; then
+		AC_MSG_ERROR([Please install osmocom-python to run the VTY/CTRL tests.])
 	fi
 fi
-AC_MSG_CHECKING([whether to enable VTY tests])
-AC_MSG_RESULT([$enable_vty_tests])
-AM_CONDITIONAL(ENABLE_VTY_TESTS, test "x$enable_vty_tests" = "xyes")
+AC_MSG_CHECKING([whether to enable VTY/CTRL tests])
+AC_MSG_RESULT([$enable_ext_tests])
+AM_CONDITIONAL(ENABLE_EXT_TESTS, test "x$enable_ext_tests" = "xyes")
 
 dnl Generate the output
 AM_CONFIG_HEADER(bscconfig.h)