Fix strerror() calls with negated sfifo error codes in sdl2sound and coreaudiosound
Document palcompositetest and scalerexpandtest in unittests.txt
Add display_parse_attr() tests to displaytest
Replace pixel dirty-tracking tables with address arithmetic
Initialise new_scaler/new_timex_scaler to silence -Wmaybe-uninitialized
Replace magic 768 with DISPLAY_ATTR_BYTES constant
Use DISPLAY_PIXEL_BYTES in display_dirty64()
Fix -Wstringop-overflow warning in check_partial_redraw_32()