Vendor dependencies

Let's see how I like this workflow.

vendor/memchr/Cargo.toml

@@ -0,0 +1,78 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+name = "memchr"
+version = "2.5.0"
+authors = [
+    "Andrew Gallant <jamslam@gmail.com>",
+    "bluss",
+]
+exclude = [
+    "/bench",
+    "/.github",
+    "/fuzz",
+]
+description = "Safe interface to memchr."
+homepage = "https://github.com/BurntSushi/memchr"
+documentation = "https://docs.rs/memchr/"
+readme = "README.md"
+keywords = [
+    "memchr",
+    "char",
+    "scan",
+    "strchr",
+    "string",
+]
+license = "Unlicense/MIT"
+repository = "https://github.com/BurntSushi/memchr"
+
+[profile.bench]
+debug = true
+
+[profile.release]
+debug = true
+
+[profile.test]
+opt-level = 3
+debug = true
+
+[lib]
+name = "memchr"
+bench = false
+
+[dependencies.compiler_builtins]
+version = "0.1.2"
+optional = true
+
+[dependencies.core]
+version = "1.0.0"
+optional = true
+package = "rustc-std-workspace-core"
+
+[dependencies.libc]
+version = "0.2.18"
+optional = true
+default-features = false
+
+[dev-dependencies.quickcheck]
+version = "1.0.3"
+default-features = false
+
+[features]
+default = ["std"]
+rustc-dep-of-std = [
+    "core",
+    "compiler_builtins",
+]
+std = []
+use_std = ["std"]