travis, wml test: incorporate fabi's --noaddons mode as an option

It's not necessary since travis has no add-ons but I put it there
anyways as an example to how others should run the mainline tests.

.travis.yml

@@ -63,7 +63,7 @@ script:
     - "export DISPLAY=:99.0"
     - "sh -e /etc/init.d/xvfb start"
     - if [ "$CPP_TESTS" = true ]; then time ./test; fi          # The test executor script seems to be blocking stderr, disabling for now...   time ./utils/travis/test_executor.sh; fi
-    - if [ "$WML_TESTS" = true ]; then time ./run_wml_tests -g -v -t "$WML_TEST_TIME"; fi
+    - if [ "$WML_TESTS" = true ]; then time ./run_wml_tests -g -v -c -t "$WML_TEST_TIME"; fi
     - if [ "$PLAY_TEST" = true ]; then time ./utils/travis/play_test_executor.sh; fi
 
 after_failure:

run_wml_tests

@@ -11,6 +11,7 @@ usage()
   echo -e "\t-h\tShows this help."
   echo -e "\t-v\tVerbose mode."
   echo -e "\t-w\tVery verbose mode. (Debug script.)"
+  echo -e "\t-c\tClean mode. (Don't load any add-ons. Used for mainline tests.)"
   echo -e "\t-a arg\tAdditional arguments to go to wesnoth."
   echo -e "\t-t arg\tNew timer value to use, instead of 10s as default."
   echo -e "\t-s\tDisable strict mode. By default, we run wesnoth with option"
@@ -154,6 +155,11 @@ run_test()
     opts+="--log-strict=warning "
   fi
 
+  # If running clean mode, then pass "--noaddons"
+  if [ "$CleanMode" -eq 1 ]; then
+    opts+="--noaddons "
+  fi
+
   # Assemble command
   command="$preopts"
   command+="$binary"
@@ -187,6 +193,7 @@ run_test()
 
 Verbose=0
 UnixTimeout=0
+CleanMode=0
 LoadFile="wml_test_schedule"
 BinPath="./"
 StrictMode=1
@@ -195,7 +202,7 @@ GdbBacktraceMode=0
 extra_opts=""
 basetimer=10
 
-while getopts ":hvwusdgp:l:a:t:" Option
+while getopts ":hvwcusdgp:l:a:t:" Option
 do
   case $Option in
     h )
@@ -212,6 +219,9 @@ do
         Verbose=2
       fi
       ;;
+    c )
+      CleanMode=1
+      ;;
     u )
       UnixTimeout=1
       ;;