Fix test suite under MSVC/Debug

In a Debug build, MSVC doesn't apply copy/move elision as often,
triggering a test failure.  This relaxes the test count requirements
to let the test suite pass.

tests/test_copy_move.py

diff --git a/tests/test_copy_move.py b/tests/test_copy_move.py
index 452f6fb..b73c950 100644
--- a/tests/test_copy_move.py
+++ b/tests/test_copy_move.py
@@ -29,14 +29,14 @@
     assert move_and_copy_casts(3) == 18
     assert c_m.copy_assignments + c_m.copy_constructions == 0
     assert c_m.move_assignments == 2
-    assert c_m.move_constructions == 2
+    assert c_m.move_constructions >= 2
     assert c_mc.alive() == 0
     assert c_mc.copy_assignments + c_mc.copy_constructions == 0
     assert c_mc.move_assignments == 2
-    assert c_mc.move_constructions == 2
+    assert c_mc.move_constructions >= 2
     assert c_c.alive() == 0
     assert c_c.copy_assignments == 2
-    assert c_c.copy_constructions == 2
+    assert c_c.copy_constructions >= 2
     assert c_m.alive() + c_mc.alive() + c_c.alive() == 0