rust: update regex & memchr dependencies

Bug: #5260.

rust/Cargo.toml.in

@@ -28,7 +28,7 @@ bitflags = "~1.2.1"
 byteorder = "~1.4.2"
 uuid = "~0.8.2"
 crc = "~1.8.1"
-memchr = "~2.2.1"
+memchr = "~2.4.1"
 num = "~0.2.1"
 num-derive = "~0.2.5"
 num-traits = "~0.2.14"
@@ -50,7 +50,7 @@ sha2 = "~0.9.2"
 digest = "~0.9.0"
 sha-1 = "~0.9.2"
 md-5 = "~0.9.1"
-regex = "~1.4.2"
+regex = "~1.5.5"
 lazy_static = "~1.4.0"
 base64 = "~0.13.0"