AMIGAOS: Make use of the new drawer icon

On AmigaOS the user can customize every icon including drawers.

This is a customized drawer icon for ScummVM with the original "S"
scaled on top of it.

This icon may change with further revisions of AmigaOS4 (if the
default icon images change).
CGE: Remove fallback detection.
Merge pull request #501 from raziel-/patch-3

AMIGAOS: Add and make use of a new drawer icon
MADS: Beginnings of resource loading in AnimView
MADS: Further resource entry initialization
CGE: Cleanup detection, implement fallbackDetect
CGE2: Implement fallbackDetect
CGE2: Reduce the scope of a variable
CGE2: Add some comment concerning the fallback detection in CGE2
SCUMM: Fix regression in demo versions of The Dig.
MADS: Further animation setup in AnimView
SCUMM: Correct fix for regressions in The Dig demos, and remove the hack for demos.
MADS: Phantom - add preloadsequence call in initializeGlobals
TSAGE: Fix for bug #6734 - insetUp being incorrect
MADS: Add new Animation fields needed by AnimView
MADS: Fix Animation to handle loading backgrounds as well as user interfaces
AMIGAOS: Cleanup

Comments cleanup and one case of a misused TAB
CONFIGURE: Ask for unity >= 3.8.1
Previously we asked for unity == 3.8.1, which broke things everywhere else
CONFIGURE: Use pkgconfig to get CFLAGS for Unity if not supplied

This is not necessary if we got --with-libunity-prefix= (line
1447).
That's not always the case though.
AMIGAOS: More cleanup

Another case of misused TAB