File .gitattributes artifact 40e3b3d8ef part of check-in trunk

# Documentaiton
doc/* linguist-vendored
# DOS Executables
dos/* linguist-vendored
# "Reduce" and "Standard Lisp" unavailable.
*.sl linguist-vendored
*.red linguist-vendored
# Exclude TeX to avoid misclassification.
*.tex linguist-vendored
doc/*.tex linguist-vendored