* wip multi process multi gpu dist training

* workable for p2p

* update test=develop

* change back env name test=develop

* fix alloc init

* fix cpu build test=devlop

* fix mac tests test=develop

* refine code

* refine test=develop

test=develop

test=develop

* human readable memory warns test=develop

* update test=develop

* refine test=develop

* fix build test=develop

test=develop

test=develop

Fix code to support cpplint syntax check

test=develop

- add naive executor
- fix concurrency performance issue

Use OO style to rewrite memory allocation.

* memory init

* add env

* refine anounce

* Add check for Nan

* Debug

* Add env for cc_test

* Add env for py_test and nv_test

* Remove py_test env

* Add env for py_test

* serial test_recognize_digits

* Test FLAGS_init_allocated_mem function for unit test

* Init allocated mem for op unit test

* Add env for all unit test

* Fix cpplint errors with paddle/fluid/platform/gpu_info.*

* Update

* fix gpu memory allocation policy

* refine codes

* fix code style

* follow comments

* add gflags for C++ unittest

* Add debug logs in scope, meta_cache and memory

* Add missing deps

* Make global scope not thread-safe

1. It is no need to make global scope thread-safe, since it will be
invoked in Python main thread.
2. Do not free the global scope when C++ exit. Let the OS free memories,
otherwise, we need to handle the destroy dependencies.

See
https://google.github.io/styleguide/cppguide.html#Static_and_Global_Variables

* Revert "FIX: Release CPU/GPU memory via deleter"

This reverts commit 8f80f5bc.