Introduce the mismatched_lifetime_syntaxes lint

Author: shepmaster

tests/pass/fat_ptr.rs

@@ -19,11 +19,11 @@ fn fat_ptr_via_local(a: &[u8]) -> &[u8] {
     x
 }
 
-fn fat_ptr_from_struct(s: FatPtrContainer) -> &[u8] {
+fn fat_ptr_from_struct(s: FatPtrContainer<'_>) -> &[u8] {
     s.ptr
 }
 
-fn fat_ptr_to_struct(a: &[u8]) -> FatPtrContainer {
+fn fat_ptr_to_struct(a: &[u8]) -> FatPtrContainer<'_> {
     FatPtrContainer { ptr: a }
 }