Merge pull request #805 from chkr-private/costume-fixes

EMI: costume fixes
EMI/GRIM: TextSplitter::checkString should ignore case

All other methods of TextSplitter ignore the case: the strings of the
splitted text are changed to lowercase and other strings provided via
arguments are compared case-insensitive.
Merge pull request #810 from chkr-private/smush-movie-issue

EMI/GRIM: TextSplitter::checkString should ignore case
GRIM/EMI: Fix sprite scaling with non-native screen resolutions

When mapping a sprite to a GL polygon its dimensions are scaled by the ratio
between the current screen resolution and the native game resolution. When
the polygon is rendered it is scaled again, causing sprites to be displayed
unproportionally big when using larger screen resolutions.
Merge pull request #808 from inguin/sprite-scaling

GRIM/EMI: Fix sprite scaling with non-native screen resolutions
EMI: Fix costume unloading

- use the costumeName instead of a pointer to the costume object to
  check, whether the current costume matches the requested one
- this fixes an uninitialized pointer read