make sure SMSlib compiles with more recent SDCC versions too

extra care in picking the moment for the VDP initialization

better performance loading 2bpp tiles

SMS_load2bppTiles and SMS_saveTileMapColumn added

ensure VRAM write bit on dest address

makesms and ihx2sms recompilation with SOURCE_DATE_EPOCH support

ihx2sms: Respect SOURCE_DATE_EPOCH when filling in header (#75)

assets2banks 3.4: replacing values in the data is now supported

assets2banks README.md minor fixes

assets2banks 3.3: discarding sections of data from assets now supported

Merge remote-tracking branch 'origin/master'

better crt0_sg

bettercrt0_sg

crt0_sms no longer clears the whole RAM, only what's required

SGlib_CV and crt0_cv updated (for ColecoVision)