Per XLS-0095, we are taking steps to rename ripple(d) to xrpl(d).
C++ include guards are used to prevent the contents of a header file from being included multiple times in a single compilation unit. This change renames all `RIPPLE_` and `RIPPLED_` definitions, primarily include guards, to `XRPL_`. It also provides a script to allow developers to replicate the changes in their local branch or fork to avoid conflicts.
