syntax: absorb utf8-ranges crate

This commit brings the utf8-ranges crate into regex-syntax as a utf8
sub-module.

This was done because it was observed that utf8-ranges is effectively
unused outside the context of regex-syntax. It is a very small amount of
code, and fits alongside the rest of regex-syntax. In particular, anyone
building a regex engine using regex-syntax will likely need this code
anyway.

Cargo.toml

@@ -33,8 +33,6 @@ memchr = "2.2.1"
 thread_local = "0.3.6"
 # For parsing regular expressions.
 regex-syntax = { path = "regex-syntax", version = "0.6.9" }
-# For compiling UTF-8 decoding into automata.
-utf8-ranges = "1.0.1"
 
 [dev-dependencies]
 # For examples.

regex-debug/Cargo.toml

@@ -16,4 +16,3 @@ regex = { version = "1.1", path = ".." }
 regex-syntax = { version = "0.6", path = "../regex-syntax" }
 serde = "1"
 serde_derive = "1"
-utf8-ranges = "1"

regex-debug/src/main.rs

@@ -4,7 +4,6 @@ extern crate regex_syntax as syntax;
 extern crate serde;
 #[macro_use]
 extern crate serde_derive;
-extern crate utf8_ranges;
 
 use std::error;
 use std::io::{self, Write};
@@ -207,8 +206,8 @@ fn cmd_compile(args: &Args) -> Result<()> {
 
 fn cmd_utf8_ranges(args: &Args) -> Result<()> {
     use syntax::hir::{self, HirKind};
+    use syntax::utf8::Utf8Sequences;
     use syntax::ParserBuilder;
-    use utf8_ranges::Utf8Sequences;
 
     let hir = ParserBuilder::new()
         .build()

regex-syntax/src/lib.rs

@@ -107,6 +107,7 @@ pub mod hir;
 mod parser;
 mod unicode;
 mod unicode_tables;
+pub mod utf8;
 
 /// Escapes all regular expression meta characters in `text`.
 ///