Fix a number of warnings cropping up on nightly Rust (#2767)

Various small issues here and there, nothing major

cranelift/codegen/src/isa/unwind/winx64.rs

@@ -46,7 +46,7 @@ impl<'a> Writer<'a> {
 
 /// The supported unwind codes for the x64 Windows ABI.
 ///
-/// See: https://docs.microsoft.com/en-us/cpp/build/exception-handling-x64
+/// See: <https://docs.microsoft.com/en-us/cpp/build/exception-handling-x64>
 /// Only what is needed to describe the prologues generated by the Cranelift x86 ISA are represented here.
 /// Note: the Cranelift x86 ISA RU enum matches the Windows unwind GPR encoding values.
 #[allow(dead_code)]
@@ -195,7 +195,7 @@ pub(crate) trait RegisterMapper<Reg> {
 /// Represents Windows x64 unwind information.
 ///
 /// For information about Windows x64 unwind info, see:
-/// https://docs.microsoft.com/en-us/cpp/build/exception-handling-x64
+/// <https://docs.microsoft.com/en-us/cpp/build/exception-handling-x64>
 #[derive(Clone, Debug, PartialEq, Eq)]
 #[cfg_attr(feature = "enable-serde", derive(Serialize, Deserialize))]
 pub struct UnwindInfo {

cranelift/codegen/src/machinst/abi_impl.rs

@@ -102,7 +102,7 @@
 //! support the SpiderMonkey Wasm ABI.  For details of the multi-value return
 //! ABI, see:
 //!
-//! https://searchfox.org/mozilla-central/rev/bc3600def806859c31b2c7ac06e3d69271052a89/js/src/wasm/WasmStubs.h#134
+//! <https://searchfox.org/mozilla-central/rev/bc3600def806859c31b2c7ac06e3d69271052a89/js/src/wasm/WasmStubs.h#134>
 //!
 //! In brief:
 //! - Return values are processed in *reverse* order.

cranelift/codegen/src/regalloc/liverange.rs

@@ -66,7 +66,7 @@
 //! Our current implementation uses a sorted array of compressed intervals, represented by their
 //! boundaries (Block, Inst), sorted by Block. This is a simple data structure, enables coalescing of
 //! intervals easily, and shows some nice performance behavior. See
-//! https://github.com/bytecodealliance/cranelift/issues/1084 for benchmarks against using a
+//! <https://github.com/bytecodealliance/cranelift/issues/1084> for benchmarks against using a
 //! bforest::Map<Block, Inst>.
 //!
 //! ## block ordering
@@ -112,7 +112,7 @@
 //! the necessary API to make coalescing easy, nor does it optimize for our types' sizes.
 //!
 //! Even the specialized `bforest::Map<Block, Inst>` implementation is slower than a plain sorted
-//! array, see https://github.com/bytecodealliance/cranelift/issues/1084 for details.
+//! array, see <https://github.com/bytecodealliance/cranelift/issues/1084> for details.
 
 use crate::entity::SparseMapValue;
 use crate::ir::{Block, ExpandedProgramPoint, Inst, Layout, ProgramOrder, ProgramPoint, Value};