Plus42 algebraic expressions update

[Thomas Okken]

10:56 PM EST / 3:56 UTC -- New builds. Nothing very interesting yet: Fixed a crash in the matrix editor's GOTO, when the stack was empty (big stack mode only, obviously); fixed crash in DROPN in 4STK mode; fixed coordinate bounds check in AGRAPH that could cause nothing to get drawn when the object was 1 pixel from being entirely off-screen; created "adaptive" icons for Android 8 and later.

UPDATE 11:26 PM EST / 4:26 UTC -- Also restored full filesystem access in the file selection dialog for Android 10.