Bug/bts1831 (argc / argv)

Implements 1831

 - fix indentation
 - follow the model of must_init, build_initializer
 - only generated code if generate is set,
 - generate code "on project".
 - rename mainargs.i -> mainargs.c

Bug/bts1836 (off by one in bittree)

also change gcc_test.sh so that one can pass arguments to program
under test.