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.

1 files changed, 0 insertions, 7 deletions

diff --git a/src/parser.cc b/src/parser.cc
index 756922d..5f303c5 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -31,13 +31,6 @@ bool Parser::Load(const string& filename, string* err, Lexer* parent) {
     return false;
   }
 
-  // The lexer needs a nul byte at the end of its input, to know when it's done.
-  // It takes a StringPiece, and StringPiece's string constructor uses
-  // string::data().  data()'s return value isn't guaranteed to be
-  // null-terminated (although in practice - libc++, libstdc++, msvc's stl --
-  // it is, and C++11 demands that too), so add an explicit nul byte.
-  contents.resize(contents.size() + 1);
-
   return Parse(filename, contents, err);
 }