[VB6/VBA6] Encrypted I/O, RC4

[dilettante]

Ideas for enhancements:

• More sophisticated key generation in CryptFile.
• Open text files for append.
• Enhance ReadBytes/WriteBytes for partial-line text I/O (read/write n characters with no newline).
• Forward seek for binary reading, line skip for text reading.
• Rewind to beginning for text and binary reading.
• UTF-8 text encoding support.
• Alternative encryption algorithms.