convert all log_error_write() to log_error() and pass (log_error_st *)
use con->errh in preference to srv->errh (even though currently same)
avoid passing (server *) when previously used only for logging (errh)
quickly clear buffer instead of buffer_string_set_length(b, 0) or
buffer_reset(b). Avoids free() of large buffers about to be reused,
or buffers that are module-scoped, persistent, and reused.
(buffer_reset() should still be used with buffers in connection *con
when the data in the buffers is supplied by external, untrusted source)
More specific checks on contents of array lists. Each module using
lists now does better checking on the types of values in the list
(strings, integers, arrays/lists)
This helps prevent misconfiguration of things like cgi.assign,
fastcgi.server, and scgi.server, where source code might be
served as static files if parenthesis are misplaced.