Log Message:
gflags: updated to 2.2.2

gflags 2.2.2
This maintenance release improves life of Bazel users (no more
"config.h" leaking into global include paths), fixes build with recent \ 
MinGW
versions, and silences a number of static code analyzer and compiler warnings.
The build targets exported by the CMake configuration of this library are now
also prefixed by the package name "gflags::" following a more recent
(unwritten) CMake convention. The unprefixed target names are still supported
to avoid that dependent projects have to be modified due to this change in
imported target names.

gflags 2.2.1
Maintenance release with mainly Windows build fixes.
* Link to online documentation in README
* Include utils by file instead of CMAKE_MODULE_PATH search
* Remove unused program_name variable
* Enable language C for older CMake versions when needed
* Changed include directory in bazel build
* Mark single argument constructors in mutex.h as explicit
* Use inttypes.h on VC++ 2013 and later
* Fix statically linked gflags library with MSVC
* Modify installation paths on Windows for vcpkg
* Fix static initialization order fiasco caused by global registry lock
* Fix use of ARGC in CMake macros
* Static code analyzer error regarding strncmp with empty kRootDir
* Check HAVE_STDINT_H or HAVE_INTTYPES_H for older MSVC versions