Split out the typevar module.

- cdsl.typevar defines TypeVar and TypeSet classes.

docs/metaref.rst

@@ -102,7 +102,7 @@ instances that refer to a *type variable* instead of a concrete value type.
 Polymorphism only works for SSA value operands. Other operands have a fixed
 operand kind.
 
-.. autoclass:: cretonne.typevar.TypeVar
+.. autoclass:: cdsl.typevar.TypeVar
     :members:
 
 If multiple operands refer to the same type variable they will be required to

lib/cretonne/meta/cretonne/__init__.py

@@ -23,7 +23,7 @@ except ImportError:
     TYPE_CHECKING = False
 
 if TYPE_CHECKING:
-    from .typevar import TypeVar  # noqa
+    from cdsl.typevar import TypeVar  # noqa
 
 
 # Defining instructions.

lib/cretonne/meta/cretonne/base.py

@@ -6,8 +6,8 @@ support.
 """
 from __future__ import absolute_import
 from cdsl.operands import VARIABLE_ARGS
+from cdsl.typevar import TypeVar
 from . import Operand, Instruction, InstructionGroup
-from .typevar import TypeVar
 from base.types import i8, f32, f64, b1
 from base.immediates import imm64, uimm8, ieee32, ieee64, immvector
 from base.immediates import intcc, floatcc