Fix RETURN macros

Remove trailing semicolon

Fix RETURNNULL(X) -- was not executing X at all
Improve overlay buffer ob_xxx() primitives

All ob_append_xxx(b,...) functions return void

ob_makespace() returns 1 if successful, 0 if not

Add ob_overrun(b) predicate to check for overrun after any number of
appends
Fix link state routing timing logic

Avoid calling schedule() with zero alarm time
Add 'debug.overlaybuffer' logging

Instrument all ob_xxx() primitives with __whence
Improve MDP debug logging
Update 'dnaprotocol' debug flags
Add 'debug.subscriber' config option

Add debug logging to find_subscriber() function
strbuf_append_sockaddr_in()
Improve dummy file Read/Write debug logging
Remove bogus ERROR messages from Batphone log

Improve overlay buffer primitives to eliminate bugus logged ERRORs
"ob_makespace() failed" and "could not append payload of N bytes" and
also add buffer overflow checks to more packet construction code.

Fix link state timing logic to eliminate logged ERROR "Alarm `link_send`
tried to schedule a deadline 1343871867115ms ago"

Improve debug logging of some MDP and dummy interface read/write code

Add 'debug.overlaybuffer' and 'debug.subscriber' config options