...by adding the -projection-no-head-constant flag to the build settings.

Move everything into the new namespace starting with 'prosa' rather
than the bland 'rt'.

No need to re-generate an unchanging file from scratch.

- Remove Require declarations from Modules.
- Small fixes due to changes in the type checker.
- Generate _CoqProject with Makefile and remove spurious warnings from ssreflect.