Fixing text caret issue

Everything drawn in MLI goes through the Image class, which takes the
game surface resolution into account - except for the caret in prompt
overlays, which is just drawn as a rectangle.  This fixes things by
making the caret take the screen scale into account as well.
Fixing uninitialized variable in DialogCharacter::OneTimeEmotion

leadInTime in DialogCharacter::OneTimeEmotion, if it doesn't exist in
the XML definition, never actually gets initialized to anything.  We
should initialize it to 0.  (Thanks to cabbage, who pointed this out on
the forums.)