globset: polishing

This brings the code in line with my current style. It also inlines the
dozen or so lines of code for FNV hashing instead of bringing in a
micro-crate for it. Finally, it drops the dependency on regex in favor
of using regex-syntax and regex-automata directly.

crates/globset/src/fnv.rs

@@ -0,0 +1,30 @@
+/// A convenience alias for creating a hash map with an FNV hasher.
+pub(crate) type HashMap<K, V> =
+    std::collections::HashMap<K, V, std::hash::BuildHasherDefault<Hasher>>;
+
+/// A hasher that implements the Fowler–Noll–Vo (FNV) hash.
+pub(crate) struct Hasher(u64);
+
+impl Hasher {
+    const OFFSET_BASIS: u64 = 0xcbf29ce484222325;
+    const PRIME: u64 = 0x100000001b3;
+}
+
+impl Default for Hasher {
+    fn default() -> Hasher {
+        Hasher(Hasher::OFFSET_BASIS)
+    }
+}
+
+impl std::hash::Hasher for Hasher {
+    fn finish(&self) -> u64 {
+        self.0
+    }
+
+    fn write(&mut self, bytes: &[u8]) {
+        for &byte in bytes.iter() {
+            self.0 = self.0 ^ u64::from(byte);
+            self.0 = self.0.wrapping_mul(Hasher::PRIME);
+        }
+    }
+}