The attached v1-0001 patch adjusts some code in stringinfo.h to find
misusages of the appendStringInfo functions. I don't intend to commit
that, but I do intend to commit the patch for the new misusages that
it found, which is also attached.
This is along the same lines as 8b26769bc, f736e188c, 110d81728 and 8abc13a88.
David