Resolve some needless_lifetimes clippy lints

    warning: the following explicit lifetimes could be elided: 'a
      --> src/to_tokens.rs:78:6
       |
    78 | impl<'a, T: ?Sized + ToTokens> ToTokens for &'a T {
       |      ^^                                      ^^
       |
       = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_lifetimes
       = note: `-W clippy::needless-lifetimes` implied by `-W clippy::all`
       = help: to override `-W clippy::all` add `#[allow(clippy::needless_lifetimes)]`
    help: elide the lifetimes
       |
    78 - impl<'a, T: ?Sized + ToTokens> ToTokens for &'a T {
    78 + impl<T: ?Sized + ToTokens> ToTokens for &T {
       |

    warning: the following explicit lifetimes could be elided: 'a
      --> src/to_tokens.rs:84:6
       |
    84 | impl<'a, T: ?Sized + ToTokens> ToTokens for &'a mut T {
       |      ^^                                      ^^
       |
       = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_lifetimes
    help: elide the lifetimes
       |
    84 - impl<'a, T: ?Sized + ToTokens> ToTokens for &'a mut T {
    84 + impl<T: ?Sized + ToTokens> ToTokens for &mut T {
       |

    warning: the following explicit lifetimes could be elided: 'a
       --> src/runtime.rs:105:14
        |
    105 |     impl<'q, 'a, T: RepAsIteratorExt<'q> + ?Sized> RepAsIteratorExt<'q> for &'a T {
        |              ^^                                                              ^^
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_lifetimes
    help: elide the lifetimes
        |
    105 -     impl<'q, 'a, T: RepAsIteratorExt<'q> + ?Sized> RepAsIteratorExt<'q> for &'a T {
    105 +     impl<'q, T: RepAsIteratorExt<'q> + ?Sized> RepAsIteratorExt<'q> for &T {
        |

    warning: the following explicit lifetimes could be elided: 'a
       --> src/runtime.rs:113:14
        |
    113 |     impl<'q, 'a, T: RepAsIteratorExt<'q> + ?Sized> RepAsIteratorExt<'q> for &'a mut T {
        |              ^^                                                              ^^
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_lifetimes
    help: elide the lifetimes
        |
    113 -     impl<'q, 'a, T: RepAsIteratorExt<'q> + ?Sized> RepAsIteratorExt<'q> for &'a mut T {
    113 +     impl<'q, T: RepAsIteratorExt<'q> + ?Sized> RepAsIteratorExt<'q> for &mut T {
        |

src/runtime.rs

@@ -102,15 +102,15 @@ pub mod ext {
         fn quote_into_iter(&'q self) -> (Self::Iter, HasIter);
     }
 
-    impl<'q, 'a, T: RepAsIteratorExt<'q> + ?Sized> RepAsIteratorExt<'q> for &'a T {
+    impl<'q, T: RepAsIteratorExt<'q> + ?Sized> RepAsIteratorExt<'q> for &T {
         type Iter = T::Iter;
 
         fn quote_into_iter(&'q self) -> (Self::Iter, HasIter) {
             <T as RepAsIteratorExt>::quote_into_iter(*self)
         }
     }
 
-    impl<'q, 'a, T: RepAsIteratorExt<'q> + ?Sized> RepAsIteratorExt<'q> for &'a mut T {
+    impl<'q, T: RepAsIteratorExt<'q> + ?Sized> RepAsIteratorExt<'q> for &mut T {
         type Iter = T::Iter;
 
         fn quote_into_iter(&'q self) -> (Self::Iter, HasIter) {

src/to_tokens.rs

@@ -75,13 +75,13 @@ pub trait ToTokens {
     }
 }
 
-impl<'a, T: ?Sized + ToTokens> ToTokens for &'a T {
+impl<T: ?Sized + ToTokens> ToTokens for &T {
     fn to_tokens(&self, tokens: &mut TokenStream) {
         (**self).to_tokens(tokens);
     }
 }
 
-impl<'a, T: ?Sized + ToTokens> ToTokens for &'a mut T {
+impl<T: ?Sized + ToTokens> ToTokens for &mut T {
     fn to_tokens(&self, tokens: &mut TokenStream) {
         (**self).to_tokens(tokens);
     }