icu wants c++11

[Thomas Klausner <tk%giga.or.at@localhost>]

Since the last update, icu uses a C++11 feature (char16_t) in an
installed header file.

Some packages stopped compiling because of that, and since it's a
property of a header installed by icu, I added "CXXFLAGS+=-std=c++11"
to icu's bl3.mk file.

However, that breaks other packages like musicpd (which wants C++14)
or firefox:

.../work/build/dist/include/nscore.h:145:9: error: ISO C++ forbids declaration of 'typeof' with no type [-fpermissive]

So basically, I need a setting that says "at least C++11 for
everything that uses this".

I'm not really sure if there even is a reasonable way to do that.

Any suggestions?
 Thomas