STL rework

- fixed lots of bugs
- overlay libraries work correctly and reliably
- the STL is an overlay library
- examples updated

src/bin/cli/mod.rs

@@ -0,0 +1,2 @@
+mod prompt;
+pub use prompt::cmd_prompt;

src/bin/cli/prompt.rs

@@ -0,0 +1,11 @@
+use std::io::{self, Error, Write};
+
+pub fn cmd_prompt(prompt: &str) -> Result<(String, Vec<String>), Error> {
+  print!("{}", prompt);
+  io::stdout().flush()?;
+  let mut cmdln = String::new();
+  io::stdin().read_line(&mut cmdln)?;
+  let mut segments = cmdln.split(' ');
+  let cmd = if let Some(cmd) = segments.next() { cmd } else { "" };
+  Ok((cmd.to_string(), segments.map(str::to_string).collect()))
+}