repo: move all source code in crates directory

The top-level listing was just getting a bit too long for my taste. So
put all of the code in one directory and shrink the large top-level mess
to a small top-level mess.

NOTE: This commit only contains renames. The subsequent commit will
actually make ripgrep build again. We do it this way with the naive hope
that this will make it easier for git history to track the renames.
Sigh.

crates/searcher/examples/search-stdin.rs

@@ -0,0 +1,37 @@
+extern crate grep_regex;
+extern crate grep_searcher;
+
+use std::env;
+use std::error::Error;
+use std::io;
+use std::process;
+
+use grep_regex::RegexMatcher;
+use grep_searcher::sinks::UTF8;
+use grep_searcher::Searcher;
+
+fn main() {
+    if let Err(err) = example() {
+        eprintln!("{}", err);
+        process::exit(1);
+    }
+}
+
+fn example() -> Result<(), Box<dyn Error>> {
+    let pattern = match env::args().nth(1) {
+        Some(pattern) => pattern,
+        None => {
+            return Err(From::from(format!("Usage: search-stdin <pattern>")))
+        }
+    };
+    let matcher = RegexMatcher::new(&pattern)?;
+    Searcher::new().search_reader(
+        &matcher,
+        io::stdin(),
+        UTF8(|lnum, line| {
+            print!("{}:{}", lnum, line);
+            Ok(true)
+        }),
+    )?;
+    Ok(())
+}