Build ninja with C++11 (#2089)

* Build ninja with C++11

In order to allow future use of std::chrono to make the stats code
portable it is desirable to compile with C++11. Doing so also allows use
of std::unordered_map, and reduces the number of #ifdefs in the ninja
source code.

Switching to C++11 requires modifying both CMakeLists.txt and
configure.py, for MSVC and for other build systems. For MSVC the
required change is adding /Zc:__cplusplus to tell the compiler to
give a more accurate value for the __cplusplus macro. For other
platforms the change is to add -std=c++11 or the CMake equivalent.

This change makes some progress towards resolving issue #2004.

* Delete code and instructions

C++11 guarantees that string::data() gives null-terminated pointers, so
explicitly adding a null terminator is no longer needed.

The Google C++ Style Guide already recommends avoiding unnecessary use
of C++14 and C++17 so repeating this in CONTRIBUTING.md is not critical.

These changes both came from PR-review suggestions.

* Only set cxx_std_11 if standard is 98

* Return to unconditional target_compile_features use

After much discussion it sounds like using target_compile_features
unconditionally is best.

0 files changed, 0 insertions, 0 deletions