Log Message:
Update ruby-eventmachine to 1.2.3.

# Changelog

## 1.2.3 (February 22, 2017)
* Pure Ruby: Add get_sockname [#308, #772]
* Fix segfault when an Exception is raised from unbind callback [#765, #766]
* Allow destructors to throw when compiling in >= C++11 [#767]

## 1.2.2 (January 23, 2017)
* Java: Fix Fixnum deprecated warning in Ruby 2.4+ [#759]
* Fix uncaught C++ exception in file watcher and raise InvalidSignature [#512, #757]
* Fix connection count off-by-one for epoll and kqueue [#750]
* Fix uninitialized variable warning in EM::P::HttpClient [#749]
* Fix missing initial value for EventableDescriptor NextHeartbeat [#748]
* Fix hostname resolution on Solaris, Ilumos, SmartOS, et al [#745, #746]
* Improve reliability of tests, reduce public Internet accesses in tests [#656, \ 
#666, #749]

## 1.2.1 (November 15, 2016)
* Throw strerror(errno) when getsockname or getpeername fail [#683]
* Use a single concrete implementation of getpeername/getsockname, the rest pure \ 
virtuals [#683]
* Use gai_strerror to get the failure string from getaddrinfo [#744]
* Fix deregistering descriptor when using KQUEUE [#728]
* Fix to enable to work an example code in EM::Pool [#731]
* LineText2: Add regular expression delimiter support [#706]
* Pure Ruby: EM rescue ECONNREFUSED on initial TCP connect [#741]
* Pure Ruby: EM SSL (working start_tls) [#712]
* Pure Ruby: EM fixes [#707]
* Java: Use Acceptors to get peer and sock names if not present in Connections [#743]