Re: Issue 5720: Fix C++11 option (issue 579270051 by address@hidden)

[trueroad]

In `-std=c++11`, most POSIX functions/definitions cannot be used.
Also `putenv ()` and `chroot ()` cannot be used.
These missing raises error in compiling LilyPond.

We can define `M_PI` if there is no `M_PI` definition.
We can implement `strdup ()` alternative by using only strict C++11
standard functions.

If I understand correctly, implementing `getenv ()` or `chroot ()` is
very difficult.


https://codereview.appspot.com/579270051/