[#23] Add logfile_mode to control logfile permissions

Fix mocklog unused arguments

Fix redefinition of _XOPEN_SOURCE.

Don't call RAW_VLOG with locking vmodule_lock

SetVLOGLevel locks vmodule_lock however RAW_VLOG at the end also implicitly locks it via InitVLOG3__.
This causes deadlock/segfault.

fixes #29 

delete LogDestination::sinks_ at DeleteLogDestinations(). 

fixes #8 

Add CMake support. closes #4 

Under Debian Jessie, I get a warning about redefining _XOPEN_SOURCE
which is easy to fix.

SetVLOGLevel locks vmodule_lock however RAW_VLOG at the end also implicitly locks it via InitVLOG3__.

This causes deadlock/segfault.

Guard GOOGLE_PREDICT_TRUE|FALS with #ifndef to avoid collision with other google opensource projects like protobuf.

fixes #8 AddLogSink memory leak

LOG_STRING: use std::vector and std::string.

Previously, plain vector and string were used.
This assumed that there were "using" directives or
declarations before the macro was used.  This will
not always be the case.

Adds color output support for tmux terminals

Fix x64/Debug build on MSVS

Also add a CONTRIBUTING.md, that GitHub will link to in the pull request
creation page.

glog: release 0.3.4