Made cbm_readdir() report a disk's format-code and more file-access modes.
Added more definitions to <cbm.h> for cbm_readdir(). And, improved the
header's comments. Added some ASCII-to-PetSCII character-mappings.
git-svn-id: svn://svn.cc65.org/cc65/trunk@4986 b7a2c559-68d2-44c3-8de9-860c34a00d81