fix fltk version to 1.2.20

Author: LChen

dsclient/Cargo.toml

@@ -13,5 +13,5 @@ panic = "abort"
 
 [dependencies]
 dscom = {path = "../dscom"}
-fltk-sys="1.2.9"
-fltk = { version = "1.2.10",features = ["fltk-bundled"] }
+fltk-sys="1.2.20"
+fltk = { version = "1.2.20",features = ["fltk-bundled"] }