build: print both pppd path and plugins path in configure summary

Reported-by: Michael Biebl <biebl@debian.org>

#25

configure.ac

@@ -1299,7 +1299,7 @@ echo
 echo "Features:"
 echo "  wext: $ac_with_wext"
 echo "  wifi: $enable_wifi"
-echo "  ppp: $enable_ppp ${PPPD_PLUGIN_DIR}"
+echo "  ppp: $enable_ppp ${PPPD_PATH} plugins:${PPPD_PLUGIN_DIR}"
 echo "  modemmanager-1: $with_modem_manager_1"
 echo "  ofono: $with_ofono"
 echo "  concheck: $enable_concheck"

meson.build

@@ -938,7 +938,7 @@ output += '  wifi: ' + enable_wifi.to_string() + '\n'
 output += '  iwd:  ' + enable_iwd.to_string() + '\n'
 output += '  pppd: ' + enable_ppp.to_string()
 if enable_ppp
-  output += ' ' + pppd_path
+  output += ' ' + pppd_path + ' plugins:' + pppd_plugin_dir
 endif
 output += '\n'
 output += '  modemmanager-1: ' + enable_modem_manager.to_string() + '\n'