Add a typevar_operand argument to the InstructionFormat constructor which
determines the operand used for inferring the controlling type variable.
Identify polymorphic instructions when they are created, determine if the
controlling type variable can be inferred from the typevar_operand, and verify
the use of type variables in the other operands.
Generate type variable summary in the documentation, including how the
controlling type variable is inferred.
We have a two-level type system: OperandKinds and ValueTypes. The value types
only apply to value operands, but there are many more kinds of operands:
immediate numbers, condition codes, basic block references, etc.
The Cretonne meta language is used to describe Cretonne instructions, both the
target independent ones in the base instruction set and real target
instructions.
Start by providing type definitions matching langref, and begin the meta
language reference using autodoc to pull in the PYthon definitions.
