diskfile: new property fileNo

set to 1 .. n by mkd64 in collectFiles()
mkd64: add interface for suggesting options
mkd64: code for automatic suggestions
code for multiple passes
reload modules for new pass
new IModule method imageComplete()

- called when all files are written to the image, to give modules a chance
  to suggest better options
several suggestion handling bugfixes

- format string corrected for printing
- use local copy of argument string
- added missing 'break' for -P option
show error message and abort when disk is full
windows bugfix: read option file in binary mode

this ensures the bytes read equal the filesize on successful read
cbmdos: use possibility to suggest options
cbmdos: bugfix, call _reserveDirBlocks only 1 time
standard CFLAGS for Makefile

- ensure no unintended exports by using -fvisibility=hidden
- ensure MSVC compatibility by failing on declarations after statements
API Version for modules, checked while loading
add example module and makefile
mkd64 sdk -- preparations and deb installation
Makefile: new targed for creating sdk tree
fix example Makefile for modules
git-ignore sdk tree
fix compilation with MSVC
documented API version in modapi.txt