* Previous implementation did not correctly restore the warning state if initially disabled.

* Upstream Chromium local changes to symbolize.cc

Chromium has its own fork of symbolize.cc and symbolize.h, and it has
several not-yet-upstreamed changes, that are not specific to Chromium.

This patch upstreams such a changes.

  Fixed google::FindSymbol reading past end of a section
  https://chromium.googlesource.com/chromium/src/+/3dae0a2d7da309159a301e40a592692ec8431a38

  Fix -INT_MIN integer overflow in itoa_r().
  https://chromium.googlesource.com/chromium/src/+/ac4d28e9cb934e01ff16a9e67a5f387caa82719f

  Add print_unsymbolized_stack_traces gn arg.
  https://chromium.googlesource.com/chromium/src/+/6a2726776f59cdcf0090f584a15db4a1ab8c40d7

  Switch to standard integer types in base/.
  https://chromium.googlesource.com/chromium/src/+/9b6f42934e5a1e65ebfc668d91a28a6e2678a14c

* Add a build option to print unsymbolized traces

This PRINT_UNSYMBOLIZED_STACK_TRACES option to cmake, and
--enable-unsymbolized-traces option to autoconf.

The newly-released gflags 2.2.2 includes fixes to the Bazel BUILD files
that weren't in the older 2.2.1 release.

Make symbolize.cc thread safe even on shared fds

ReadFromOffset in symbolize.cc used to call lseek() + read() to read
data from fd. However, the fd may be reused for multiple symbolize
requests from multiple threads, and causes a race around the fd read
offset.

This updates it to use pread() to resolve the race.

To fix https://github.com/google/glog/issues/376

Don't crash on some forms of invalid ELF files

Fix mistype in comment

With a few tweaks, it will fail to look up symbol names in these cases
instead.

Fix errors with BUILD_SHARED_LIBS=ON for Visual Studio 2017 (fixes #343)

resolves #338

fix glog.html link to gflags repository

Delete NEWS

remove unused 10 year old empty file

Fixes Issue https://github.com/google/glog/issues/325

Fix windows logging ut

tests: fix compilation with C++17

Remove throw() commands as they were deprecated with C++11 and are
removed with C++17

just like the null pointer test.

Fix mingw cross compile

This eliminates a conflict between glog and gflags preprocessor definition of GFLAGS_NAMESPACE that can cause the gflags namespace detection to fail (fixes #317).

- check in cmake if localtime_r exists
- if localtime_r is missing (MSVC, mingw-w64 on linux) redefine it using
  localtime_s

- fix dbhelp.h include
- fix dbghelp check and link

This was previously present in
https://github.com/bazelbuild/continuous-integration, but the Bazel team
asked us to move it to our repo. It will be helpful if we need to change
the build configuration, eg to add new platforms.

Resolve missing prototype warning

Fix redefined warnings from config.h

Make int conversion explicit and fix clang warning

The issue was caused by config.h header being included from both
header files and implementation files.

Proposed solution is to have regular header guard in the generated
config.h. Benefit of this solution is that it's least intrusive.
Downside is that it only solves issue for CMake build system, and
autoconf one is not fixed since header template is automatically
generated by autoheader who does not add header guard.