"IN" now sometimes reserved

Recent versions of some Pick-based systems now consider IN to be a reserved word in BASIC. If you use such a release, you will be unable to compile the BTPINS subroutine, because it uses a variable named IN.

To compile BTPINS, just change the variable IN to some other unused name (such as INX) in lines 18, 19, 23, and 24 of the BTPINS subroutine.