Merge error and my_error

There are two (ok, there are more, but let's start with these) error headers/impls - error.h and my_error.h. It is unclear a) what the difference is b) what they are to be used for. error.h and my_error.h should be merged into just error.h. Also, there is a current clear way to print server error messages to standard err (errmsg_printf) but there seem to be a bazillion ways to send errors to the client (one of which seems to be in error.h, the other of which seems to be in my_error.h) Cleaning all of this up would be fantastic.