Upgrade rust/crates/regex to 1.5.4

Test: make
Change-Id: I0eab39246dc2aea41a62c15661e350b490f06c1d
diff --git a/src/pikevm.rs b/src/pikevm.rs
index 299087d..9a14240 100644
--- a/src/pikevm.rs
+++ b/src/pikevm.rs
@@ -17,11 +17,11 @@
 
 use std::mem;
 
-use exec::ProgramCache;
-use input::{Input, InputAt};
-use prog::{InstPtr, Program};
-use re_trait::Slot;
-use sparse::SparseSet;
+use crate::exec::ProgramCache;
+use crate::input::{Input, InputAt};
+use crate::prog::{InstPtr, Program};
+use crate::re_trait::Slot;
+use crate::sparse::SparseSet;
 
 /// An NFA simulation matching engine.
 #[derive(Debug)]
@@ -231,7 +231,7 @@
         at: InputAt,
         at_next: InputAt,
     ) -> bool {
-        use prog::Inst::*;
+        use crate::prog::Inst::*;
         match self.prog[ip] {
             Match(match_slot) => {
                 if match_slot < matches.len() {
@@ -300,7 +300,7 @@
         // traverse the set of states. We only push to the stack when we
         // absolutely need recursion (restoring captures or following a
         // branch).
-        use prog::Inst::*;
+        use crate::prog::Inst::*;
         loop {
             // Don't visit states we've already added.
             if nlist.set.contains(ip) {