changes to echo example's internal API
extract socket write buffer API from echo example
bugfix: using library path's len before locking
delete obsoleted message type
rough support for current running process
reorder function definitions
add support to inject builtin service
set running process for service's delete function
exported API changed:
 * weenet_process_self() to retrieve current running process
 * weenet_process_pid(p) to get process's pid
bugfix: increase monitoring process's references
Merge branch 'develop' into running_process

Conflicts:
	src/process.c
rewrite process monitor/demonitor to enforce restriction
only called by current running process
Merge branch 'library_inject' into develop
Merge branch 'running_process' into develop
add 'const' qualifier to weenet_library_inject's interface parameter
API(weenet_process_suicide) to retire self
rewrite timer module using algorithm from skynet
(https://github.com/cloudwu/skynet)
Merge branch 'timer_rewrite' into develop
Merge branch 'develop'