9228cbbd1e
"make clean" was deleting "doc/*.pdf", despite the fact that there were two comments (one above and one below) stating that it did not. Since doc/crypt.pdf is checked into git, running "make clean" made my git state dirty, which seems undesirable. I took sort of a compromise position and had "make clean" continue to delete any other .pdf files in doc (such as refman.pdf), but explicitly not delete crypt.pdf.
See doc/crypt.pdf