Allow building wheels for free-threaded Python

They cannot use the limited API, but we can build version-specific
wheels.

Author: jlaine

.github/workflows/tests.yml

@@ -109,8 +109,6 @@ jobs:
           CIBW_BEFORE_BUILD_WINDOWS: scripts\build-libsrtp.bat C:\cibw\vendor
           CIBW_ENVIRONMENT: CFLAGS=-I/tmp/vendor/include LDFLAGS=-L/tmp/vendor/lib PKG_CONFIG_PATH=/tmp/vendor/lib/pkgconfig
           CIBW_ENVIRONMENT_WINDOWS: INCLUDE=C:\\cibw\\vendor\\include LIB=C:\\cibw\\vendor\\lib
-          # The limited API is not available on free-threaded builds.
-          CIBW_SKIP: 'cp3??t-*'
           CIBW_TEST_COMMAND: python -m unittest discover -s {project}/tests
         shell: bash
         run: |

setup.py

@@ -6,7 +6,7 @@ class bdist_wheel_abi3(bdist_wheel):
     def get_tag(self):
         python, abi, plat = super().get_tag()
 
-        if python.startswith("cp"):
+        if python.startswith("cp") and not python.endswith("t"):
             return "cp310", "abi3", plat
 
         return python, abi, plat