Add more standard cursors

This adds the standard cursors for diagonal and omnidirectional
resize/move and operation-not-allowed.  It also adds new (better?) names
for the horizontal and vertical resize/move and pointing hand cursors.

References:
 - https://developer.apple.com/documentation/appkit/nscursor
 - https://stackoverflow.com/questions/10733228/
 - https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-setsystemcursor
 - https://freedesktop.org/wiki/Specifications/cursor-spec/
 - https://tronche.com/gui/x/xlib/appendix/b/

Related to #427.

src/init.c

@@ -189,6 +189,8 @@ void _glfwInputError(int code, const char* format, ...)
             strcpy(description, "The requested format is unavailable");
         else if (code == GLFW_NO_WINDOW_CONTEXT)
             strcpy(description, "The specified window has no context");
+        else if (code == GLFW_CURSOR_UNAVAILABLE)
+            strcpy(description, "The specified cursor shape is unavailable");
         else
             strcpy(description, "ERROR: UNKNOWN GLFW ERROR");
     }