only signalhandler_unittest.cc uses "using namespace gflags".
others use "using namespace GFLAGS_NAMESPACE", so
signalhandler_unittest.cc does the same way.

fixes #62

The POSIX function fdopen is deprecated.
Use the ISO C++ conformant _fdopen instead.
https://msdn.microsoft.com/library/ms235351.aspx

fixes #73

FAILED macro is for HRESULT, not for HANDLE.
FindFirstFile returns INVALID_HANDLE_VALUE when error or not found.
https://msdn.microsoft.com/library/windows/desktop/aa364418(v=vs.85).aspx

fixes #79

FlushLogFilesUnsafe would be called in FailureSignalHandler,
so should avoid calling new/malloc, which are not signal safe.

fixes #78

Reset SIGABRT action only if FailureSignalHandler is installed.

When I set my own signal handler to SIGABRT, it did not executed
with CHECK.  That is because SIGABRT handler is reset to default
just before glog calls abort.
Let me make it reset only if the handler is what glog installed
i.e. FailureSignalHandler.

Fix missing public include directory

Fix double-free in unit test on Windows.

Link libpthread when necessary in CMake builds

Path "<prefix>/include" will not be added to the headers search of dependent
targets without specifying INSTALL_INTERFACE, i.e. compilation
will fail with error:

  "fatal error: 'glog/logging.h' file not found".

The LOG_SYSRESULT refers to result twice.  Since, in this test,
result expands to FindClose(handle), the handle was being freed twice.

Fixed warning caused by policy CMP0063 introduced in CMake 3.3

Allow to disable multithreading support using CMake

[#23] Add logfile_mode to control logfile permissions

This commit additionally enables threading for win32 by default.

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