[patch] clean up C/C++ string and character literal highlighting

A few bugs with C and C++ syntax highlighting: 1. In C mode, if c_no_c11 is set, then the highlighting of u8"foo" depends on c_no_cformat. If c_no_cformat is on, it gets highlighted even though u8"foo" is not a valid string literal pre-C11. 2. In C++ mode, if c_no_c11 is set, then (u8"foo") doe

How are we going to deal with C++14 features in syntax highlighting?

cpp.vim has a lot of if statements like this: if !exists("cpp_no_cpp11") ... endif for C++11-only features. C++14 adds binary literals and digit separators and I'm interested in adding these to cpp.vim. In analogy, should I just wrap them in if !exists("cpp_no_cpp14") ... endif blocks? -- -