Add Safari impersonation support to libcurl

Safari can now be imperonsated with libcurl using
curl_easy_impersonate() with the "safari15_3" target or by setting the
env var CURL_IMPERSONATE to "safari15_3".

curl patch from
https://github.com/lwthiker/curl/commit/0340cd8b3e0f85ba1105d75587e36c45c5b3f2bb

tests/test_impersonate.py

@@ -149,6 +149,14 @@ class TestImpersonation:
             },
             "edge_98.0.1108.62_win10"
         ),
+        (
+            "./minicurl",
+            {
+                "LD_PRELOAD": "./chrome/libcurl-impersonate.so",
+                "CURL_IMPERSONATE": "safari15_3"
+            },
+            "safari_15.3_macos11.6.4"
+        ),
         (
             "./minicurl",
             {