GUI: Redraw the popup widget when a the selection changes

Otherwise, it will look like the value hasn't changed until the
widget is redrawn for other reasons, e.g. by mouse-over.

Incidentally, does anyone know why handleMouseDown() calls
sendCommand() when the selection changes, while handleMouseWheel()
does not?
GUI: Change value by one on mouse wheel, not by one pixel

On file-grained sliders, changing the value by one pixel was
unpredictable because it wouldn't change by the same amount every
time. (And of course, some values were not possible to set.)

On course-grained sliders, changing the value by one pixel would
sometimes not change it at all, causing the slider to seem stuck.

Now the slider can be set to any value.
NEWS: Document slider mousewheel change

It wasn't obvious that the feature was there at all, so now it is
at least mentioned somewhere.
GUI: Notify when popup widget changes by mousewheel

This is consistent with the notification when the widget changes by
clicking. As far as I can tell, that notification was added shortly
before mouse wheel handling was added. It missing from the mouse
wheel handler was presumably just an oversight.
GUI: Don't allow changing disabled popup widgets with mouse wheel

This was another inconsistency between changing the widget by
clicking and changing it with the mouse wheel. Hopefully the last
one, though.
MT32: Move the ROM file deletion code to the ScummVM MT32 driver

This removes the custom ScummVM file deletion code in the munt code
MT32: Add missing initialization code

This code wasn't added when syncing with the official munt codebase
ANDROID: Minor fixes to build-specific makefile.

This fixes two minor issues when trying to cross-compile to Android on
Win32 using the Win32 Android SDK/NDK and MinGW shell.

However, this is still no working as DX and APKBUILDER are batch files
in the Win32 SDK (which then call the real Java tools) and these fail
to run in shell. However, using "cmd /C" also fails as the paths in the
parameters have unix, rather than native separators. Unsure how to fix.
SCI32: Add some notes about KScrollWindow/Add
SCI32: Add notes about KScrollWindow/Where,Go
SCI32: Add more KScrollWindow notes
SCI32: Add more KScrollWindow notes