Fixing compilation

Update compilation for PB 2.5, change INSTALL to INSTALL.md to prevent
clashes for OSX's case-insensitive filesystem
I'm not certain this change is correct by itself. I assume it was done to fix a build problem. `AND` and `MULTIPLY` may actually be intended to be aliases, since they are sort of the same operation. In particular, this switch probably needs to gain another case:

https://github.com/a4/a4/blob/e1de89260cb3894908f1d01dfacea125abc79da9/a4io/src/message.cpp#L272-L273