close-blockfile
parse-word r/w create-file abort" failed to create block-file"
set-blockfile
dup b/buf m* blockhandle resize-file
abort" unable to create a file of that size"
empty-buffers
0 do i wipe loop
flush
win32forth uses a system-filedescriptor where -1 means unused
in the BLOCKHANDLE, but we use a "FILE*"-like structure, so NULL
means NOT-IN-USE. Here we set it.