Adds command-line options -y and -n to cmsMake
cmsMake: do not set "assume" as global, but pass it in the calls stack.
cmsMake: even when assuming the answer, print the question anyway.

It is (TTBOMK) a common pattern and it helps understanding what's
going on.
Change cmsMake to also create a binary compiled with -DEVAL (sol/${NAME}_EVAL), and to use it for test_${NAME}.
cmsMake: fix some flaws in the _EVAL mechanism (as well as some previous bugs).
Allows generators and validators to be in C / C++ / Pascal too.
cmsMake: small fixes.
Change cmsMake to use argparse instead of the deprecated optparse
Allows compiled programs to use syscall 'dup3', as it already is in ./cms/grading/__init__.py