C++ falls back to standard syntax on recent Sublime Text 3 dev builds

[abusalimov]

Other languages derived from C (like C++ and Objective C) don't need their syntaxes to be changed to something special: they usually extend source.c under the hood, which is now provided by C Improved syntax.

This part of the README is not true at least on ST3 build 3109. The standard C++ grammar still includes source.c, but the standard C is used for that source.c instead of the C Improved grammar.

A probable reason is mentioned here:

Note that while Sublime Text supports both .sublime-syntax and .tmLanguage files, it's not possible to include a .tmLanguage file within a .sublime-syntax one.