message: doc: Add note about new build/test requirements to release notes
  [skip ci]
diff: @@ -41,6 +41,17 @@ Example item
  Example text.
  +
  +C++11
  +-----
  +
  +Various code modernizations have been done. The Bitcoin Unlimited code base has
  +started using C++11. This means that a C++11-capable compiler is now needed for
  +building. Effectively this means GCC 4.7 or higher, or Clang 3.3 or higher.
  +
  +When cross-compiling for a target that doesn't have C++11 libraries, configure with
  +`./configure --enable-glibc-back-compat ... LDFLAGS=-static-libstdc++`.
  +
  0.12.1 Change log
  =================
  