Fix compiler errors: add missing includes and std qualifiers.

2 jobs for feature/new_tnnmg-simplexSolver in 45 seconds (queued for 2 seconds)
Name Stage Failure
failed
dune:git--gcc Test There is an unknown failure, please try again
CMakeFiles/Makefile2:1327: recipe for target 'dune/tnnmg/functionals/test/CMakeFiles/normfunctionaltest.dir/all' failed
make[2]: *** [dune/tnnmg/functionals/test/CMakeFiles/normfunctionaltest.dir/all] Error 2
CMakeFiles/Makefile2:210: recipe for target 'CMakeFiles/build_tests.dir/rule' failed
make[1]: *** [CMakeFiles/build_tests.dir/rule] Error 2
Makefile:247: recipe for target 'build_tests' failed
make: *** [build_tests] Error 2
--- Failed to build dune-tnnmg ---
Terminating dunecontrol due to previous errors!
ERROR: Build failed: exit code 1
failed
dune:git--clang Test There is an unknown failure, please try again
CMakeFiles/Makefile2:1327: recipe for target 'dune/tnnmg/functionals/test/CMakeFiles/normfunctionaltest.dir/all' failed
make[2]: *** [dune/tnnmg/functionals/test/CMakeFiles/normfunctionaltest.dir/all] Error 2
CMakeFiles/Makefile2:210: recipe for target 'CMakeFiles/build_tests.dir/rule' failed
Makefile:247: recipe for target 'build_tests' failed
make[1]: *** [CMakeFiles/build_tests.dir/rule] Error 2
make: *** [build_tests] Error 2
--- Failed to build dune-tnnmg ---
Terminating dunecontrol due to previous errors!
ERROR: Build failed: exit code 1