Checks to build

[pietervdvn]

• [x] ADTDef: Crosvalidate names vs types (data A = A b:X | B b:Y): b should have the same type
• [x] Double type declarations in the same module
• [x] Precedence statements
  • [x] The operator should be declared in the same module
  • [x] No loops may exist
• [x] Validate typereqtable against kinds: all (applied) requirements should have the same kind

[pietervdvn]

The others are for a different time :p