windows runtime Error Fixed for gst ver1.20.4

[buYoung]

• When converting "C.CString" to "(*C.gchar"), it was removed as an unnecessary task.
• Also, I changed it to C.free when I initialized "C.CString". The reason is that the program stops in Windows OS
• I didn't remove it where "C.g_free" is required.
• Added file "element_windows.go", last factor value cast is gint64.