Hack: support project with platform_sdcc subdirectory.
Fix typo.
Attempt to integrate Kevin Thacker's cpcxfs. Works for ascii file but does not generate a AMSDOS header for a binary file.
Declare phony rules.
Integrate addhead. Use addhead + cpcxfs over iDSK by default. Use make PREFER_IDSK_OVER_CPCXFS=1 to override.
Make explicit offset in header for debug.