Add alt code to 1985/shapiro

This alt code allows one to resize the maze. Obviously if one uses -D
with a value that's not a number it will fail to compile. If it's <= 0
|| >= 5000 it will set to the default of 39.

The try.alt.sh script plays with this, first selecting a random number
(in range $RANDOM % 38) to compile with and then run. After that it runs
in an infinite loop, exiting only if input includes non-digit
characters. A value >= 5000 sets it to the default of 39 (in the code).

1985/shapiro/.gitignore

@@ -1,3 +1,4 @@
 shapiro
+shapiro.alt
 shapiro.orig
 prog.orig