by Max Cutler on WordPress.org
Removes leading and trailing whitespace from XML-RPC responses that can break some XML-RPC clients.
Uses PHP’s output buffering to buffer XML-RPC responses and strip superfluous whitespace.
Plugins, themes, and any other files executed during the WordPress load process can unintentionally emit whitespace,
such as by including a newline character after an explicit closing “?>” PHP tag instead of letting PHP auto-close the
file.