Fix #2567

__must_check is a macro mark of function return value. It let developer
must check the return value is legal or not.

1. v2.layer.parse_network does not correctly handle the generation output.
2. GatherAgentLayer does not correctly handle generation output when batch_size > 1
3. Fix CustomStackTrace for rnn group

This only fixes the issue for ATLAS
MKL is still another fix.

In the original util.cmake. enable_virtualenv.c is always regenerated when cmake files are changed, which leads to the relinking of all the targets depends on paddle_utils.

* set PYTHON_HOME outside the paddle processes.

* Also test std::vector
* Use std::vector to PadConf

 using the same implemetation as mac os.

Change-Id: Ie09fd666ca208994f22e9f83af6072f4d5e6aa1a

Also initialize glog after gflags in Util.cpp initMain()

Change-Id: I09ff062b462aa76d9f7b5f97e883b92939e6dcb2