Downgrade needless_pass_by_value to allow by default

I noticed that I suppress this lint in many of my projects.

https://github.com/search?q=needless_pass_by_value+user%3Adtolnay&type=Code
https://github.com/search?q=needless_pass_by_value+user%3Aserde-rs&type=Code

Upon further inspection, this lint has a *long* history of false
positives (and several remaining).

Generally I feel that this lint is the definition of pedantic and should
not be linted by default.

    #[derive(Debug)]
    enum How {
        ThisWay,
        ThatWay,
    }

    // Are we really better off forcing the call sites to write f(&_)...?
    fn f(how: How) {
        println!("You want to do it {:?}", how);
    }

    fn main() {
        f(How::ThatWay);
    }

Author: dtolnay

clippy_lints/src/lib.rs

@@ -509,6 +509,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
         misc_early::UNSEPARATED_LITERAL_SUFFIX,
         mut_mut::MUT_MUT,
         needless_continue::NEEDLESS_CONTINUE,
+        needless_pass_by_value::NEEDLESS_PASS_BY_VALUE,
         non_expressive_names::SIMILAR_NAMES,
         replace_consts::REPLACE_CONSTS,
         shadow::SHADOW_UNRELATED,
@@ -671,7 +672,6 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
         needless_bool::BOOL_COMPARISON,
         needless_bool::NEEDLESS_BOOL,
         needless_borrowed_ref::NEEDLESS_BORROWED_REFERENCE,
-        needless_pass_by_value::NEEDLESS_PASS_BY_VALUE,
         needless_update::NEEDLESS_UPDATE,
         neg_cmp_op_on_partial_ord::NEG_CMP_OP_ON_PARTIAL_ORD,
         neg_multiply::NEG_MULTIPLY,
@@ -809,7 +809,6 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
         misc_early::MIXED_CASE_HEX_LITERALS,
         misc_early::UNNEEDED_FIELD_PATTERN,
         mut_reference::UNNECESSARY_MUT_PASSED,
-        needless_pass_by_value::NEEDLESS_PASS_BY_VALUE,
         neg_multiply::NEG_MULTIPLY,
         new_without_default::NEW_WITHOUT_DEFAULT,
         new_without_default::NEW_WITHOUT_DEFAULT_DERIVE,

clippy_lints/src/needless_pass_by_value.rs

@@ -54,7 +54,7 @@ use crate::rustc_errors::Applicability;
 /// ```
 declare_clippy_lint! {
     pub NEEDLESS_PASS_BY_VALUE,
-    style,
+    pedantic,
     "functions taking arguments by value, but not consuming them in its body"
 }