Turn some .i files into .swig

This helps with the import / export process.

ortools/linear_solver/python/CMakeLists.txt

@@ -11,15 +11,15 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-set_property(SOURCE linear_solver.i PROPERTY CPLUSPLUS ON)
-set_property(SOURCE linear_solver.i PROPERTY SWIG_MODULE_NAME pywraplp)
-set_property(SOURCE linear_solver.i PROPERTY COMPILE_DEFINITIONS
+set_property(SOURCE linear_solver.swig PROPERTY CPLUSPLUS ON)
+set_property(SOURCE linear_solver.swig PROPERTY SWIG_MODULE_NAME pywraplp)
+set_property(SOURCE linear_solver.swig PROPERTY COMPILE_DEFINITIONS
   ${OR_TOOLS_COMPILE_DEFINITIONS} ABSL_MUST_USE_RESULT=)
 swig_add_library(pywraplp
   TYPE MODULE
   LANGUAGE python
   OUTPUT_DIR ${PYTHON_PROJECT_DIR}/linear_solver
-  SOURCES linear_solver.i)
+  SOURCES linear_solver.swig)
 
 target_include_directories(pywraplp PRIVATE ${Python3_INCLUDE_DIRS})
 set_property(TARGET pywraplp PROPERTY SWIG_USE_TARGET_INCLUDE_DIRECTORIES ON)

ortools/linear_solver/python/linear_solver.swig

@@ -11,7 +11,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// This .i file exposes the linear programming and integer programming
+// This .swig file exposes the linear programming and integer programming
 // solver. See the C++/Python codelab: .
 //
 // The python API is enriched by custom code defined here, making it
@@ -35,7 +35,7 @@
 
 %include "ortools/util/python/proto.i"
 
-%import "ortools/util/python/vector.i"
+%import "ortools/util/python/vector.swig"
 
 // We need to forward-declare the proto here, so that the PROTO_* macros
 // involving them work correctly. The order matters very much: this declaration

ortools/linear_solver/python/linear_solver_natural_api.py

@@ -13,7 +13,7 @@
 
 """Patch to the python wrapper of ../linear_solver.h providing an algebraic API.
 
-This is directly imported, and use exclusively in ./linear_solver.i. See that
+This is directly imported, and use exclusively in ./linear_solver.swig. See that
 file.
 For examples leveraging the code defined here, see ./pywraplp_test.py and
 ../../../python/linear_programming.py.

ortools/linear_solver/python/pywraplp_test.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-"""Simple unit tests for python/linear_solver.i. Not exhaustive."""
+"""Simple unit tests for python/linear_solver.swig. Not exhaustive."""
 
 import unittest
 from ortools.linear_solver import linear_solver_pb2