Traces FUNCTION with trace output going quietly to BUFFER.
When this tracing is enabled, every call to FUNCTION writes
a Lisp-style trace message (showing the arguments and return value)
into BUFFER. This function generates advice to trace FUNCTION
and activates it together with any other advice there might be.
The trace output goes to BUFFER quietly, without changing
the window or buffer configuration.
BUFFER defaults to `trace-buffer'.
To untrace a function, use `untrace-function' or `untrace-all'.
(fn FUNCTION &optional BUFFER)