Remove 1990/cmills alt code

The alt code was the version that works for modern systems before the
gets()/fgets() change (the fix being changing a read only char * to a
char []) but this is not at this time in the archive. The README.md file
refers to the archive, noting it is the original code before the bug
fix.

1990/cmills/.gitignore

@@ -1,2 +1 @@
 cmills
-cmills.alt