Update curl submodule (#317)

alexcrichton · web-flow · commit c2f56e752098 · 2020-01-08T09:26:47.000-06:00
diff --git a/curl-sys/curl b/curl-sys/curl
@@ -1 +1 @@
-Subproject commit 2e9b725f67d49a9d7a1f053fe52dd4920c9ab1ad
+Subproject commit 2cfac302fbeec68f1727cba3d1705e16f02220ad
