libstdc++-v3:

       * tests_flags.in: New file. Split out of ...
       * mkcheck.in: ... this. Move flags computation into
       tests_flags.in.
       * configure.in: Add support for tests_flags.
       * confiigure: Regenerate.

gcc/testsuite:
       * lib/g++.exp (g++_include_flags): Invoke 'tests_flags --compiler'
       instead of 'mkcheck 2'.

From-SVN: r37756