Simplifies Platform Specific Interface Creation

The interface `Config` object is now passed directly into each creation
function in order to more easily use additional options.

In addition, the linux and darwin parameters were split to better
capture different options for each platform.

params_darwin.go

@@ -0,0 +1,13 @@
+
+package water
+
+// PlatformSpecificParams defines parameters in Config that are specific to
+// macOS. A zero-value of such type is valid, yielding an interface
+// with OS defined name.
+// Currently it is not possible to set the interface name in macOS.
+type PlatformSpecificParams struct {
+}
+
+func defaultPlatformSpecificParams() PlatformSpecificParams {
+	return PlatformSpecificParams{}
+}