Added glob patterns to the syntax shapes

Bare words now represent literal file names, and globs are a different
syntax shape called "Pattern". This allows commands like `cp` to ask for
a pattern as a source and a literal file as a target.

This also means that attempting to pass a glob to a command that expects
a literal path will produce an error.

src/evaluate/evaluator.rs

@@ -114,6 +114,7 @@ fn evaluate_literal(literal: Tagged<&hir::Literal>, source: &Text) -> Tagged<Val
         hir::Literal::Number(int) => int.into(),
         hir::Literal::Size(int, unit) => unit.compute(int),
         hir::Literal::String(span) => Value::string(span.slice(source)),
+        hir::Literal::GlobPattern => Value::pattern(literal.span().slice(source)),
         hir::Literal::Bare => Value::string(literal.span().slice(source)),
     };