Document the copyright of four encryption files.
Document the copyright of four encryption files.

Document the fitz/crypt_arc4.c
             fitz/base_hash.c
             fitz/crypt_aes.c
             fitz/crypt_md5.c

copyright information.

nqv/mupdf,nqv/mupdf,nqv/mupdf,nqv/mupdf,nqv/mupdf,nqv/mupdf