Untrack scratch .pre-* backup files accidentally swept in by the tls merge commit

The merge commit (3609ed6) used git add -A to handle the large number
of deletes/renames from conflict resolution, which also picked up 22
untracked *.pre-* files - local safety-copy backups made before
editing tracked files, never meant to be committed. Untracked (kept on
disk) rather than deleted, and added *.pre-* to .gitignore so this
does not recur.

.gitignore

@@ -11,4 +11,4 @@ docs/html
 */mmap_address.bin
 .history/*
 html
-latex
+latex*.pre-*