Sam crashes trying to open more than 255 files

[aksr]

1. Have a directory with >255 files.
2. Execute sam *.
3. samterm:panic: menuins: Resource temporarily unavailable

Edit: It's a samterm's limitation in samterm.h:

`#define MAXFILES    256

Plan9port's sam doesn't have this limit, and since sam was intended to easily modify many files, I think this sam should remove it, too.

Sam's lack of internal limits and sizes is a virtue. Because it avoids all fixed-size tables and data structures, sam is able to make global changes to files that some of our other tools cannot even read. —Rob Pike, The Text Editor sam