goto; new/changed options

- support goto; correct parsing of case and default
- '-no-externs' suppresses generation of 'global' and 'extern'
- '-label <number>' takes the initial number for numbered labels
- '-seg16t' is now the old '-seg16', it generates segment declarations
compatible with 16-bit Borland/Turbo C/C++ compilers/linkers
- '-seg16' is now the same as '-seg32', except for bitness, obviously