Add mostly-empty AST module to rustc.

src/comp/fe/ast.rs

@@ -0,0 +1,12 @@
+type crate = rec( str filename );
+
+//
+// Local Variables:
+// mode: rust
+// fill-column: 78;
+// indent-tabs-mode: nil
+// c-basic-offset: 4
+// buffer-file-coding-system: utf-8-unix
+// compile-command: "make -k -C ../.. 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
+// End:
+//

src/comp/rustc.rc

@@ -4,6 +4,7 @@
 use std;
 
 mod fe {
+    mod ast;
     mod lexer;
     mod parser;
 }