Log Message:
This package once contained code that did illegal things with va_list
to try to support passing a format and va_list pair as the data for a
custom printf format in its own private printf clone.

The offending code was unused and removed upstream in 2004, but the
initial import of our package in 2005 included, without explanation, a
patch reverting this. So the code has still been there, and (being
illegal) it has now stopped compiling with clang.

Delete the offending patch section. (And while here, add comments for
the rest of this patch.)