Silver:  Remove unused CurrentA4.hh
[NEW] rot13.p68k
[DEL] v68k-rot13:  rot-13-only m68k emulator
[DEL] v68k-hello:  Hello-World-only m68k emulator

This was interesting for demonstrating the emulator runnig itself (using
a canned Hello World program in the second emulator binary so that there
was no need to open a file), but now the load primitive allows the stock
xv68k program to open files indirectly, so xv68k can emulate itself with
no issue.
[DEL] v68k-debug:  m68k emulator with debugging

This was a copy of v68k-exec with the addition of debugging output which
has since been added to xv68k.
Merge branch 'v68k-demos'