Only start using --validcache with wesnoth after at least one test
has passed.
Use --kill-after flag of unix timeout, so that if TERM fails to
stop wesnoth, a KILL will be issued.
Fixup comments.
Adds an option to the new wml test script, to use the unix
timeout command instead of wesnoth's built-in one. This is because
the built-in one is very slightly unreliable... there's a reason
killthread was deprecated in SDL unfortunately. Will leave it for
UMC but on travis will replace with unix timeout.
The unix timeout one seems consistent enough that I will enable
the empty_test timeout check for travis.
Also, adds a help listing to the wml test script.
Also, redirect some output from cout to cerr in the game...
this somewhat breaks the old script.
The old script is renamed .old
Travis points to the new script.
