Improve function names

A Tuple struct is called a Tuple struct, not an unnamed field struct, so
it makes more sense for the function to be called `make_tuple`, in line
with `make_ZST`.

src/generate/gen_enum.rs

@@ -21,7 +21,7 @@ use crate::Result;
 ///         .add_value("Unnamed")
 ///         .add_field("", "u16")
 ///         .add_field("baz", "String")
-///         .make_fields_unnamed();
+///         .make_tuple();
 /// }
 /// # generator.assert_eq("enum Foo { ZST , Named { bar : u16 , baz : String , } , Unnamed (u16 , String ,) , }");
 /// # Ok::<_, virtue::Error>(())
@@ -193,7 +193,7 @@ impl EnumValue {
     /// Make the struct fields unnamed
     ///
     /// The names of any field will be ignored
-    pub fn make_fields_unnamed(&mut self) -> &mut Self {
+    pub fn make_tuple(&mut self) -> &mut Self {
         self.value_type = ValueType::Unnamed;
         self
     }

src/generate/gen_struct.rs

@@ -59,7 +59,7 @@ impl<'a, P: Parent> GenStruct<'a, P> {
     /// # let mut generator = Generator::with_name("Fooz");
     /// generator
     ///     .generate_struct("Foo")
-    ///     .make_fields_unnamed()
+    ///     .make_tuple()
     ///     .add_field("bar", "u16")
     ///     .add_field("baz", "String");
     /// # generator.assert_eq("struct Foo (u16 , String ,) ;");
@@ -70,7 +70,7 @@ impl<'a, P: Parent> GenStruct<'a, P> {
     /// ```
     /// struct Foo(u16, String);
     /// ```
-    pub fn make_fields_unnamed(&mut self) -> &mut Self {
+    pub fn make_tuple(&mut self) -> &mut Self {
         self.struct_type = StructType::Unnamed;
         self
     }