Add scaffolding for a 'cton-util test' command.

This command accepts files and directories containing test cases to run.
Recursively searches for test files in any directory it is passed.

Actually running tests is not yet implemented.

src/tools/main.rs

@@ -10,7 +10,7 @@ use docopt::Docopt;
 use std::io::{self, Write};
 use std::process;
 
-
+mod filetest;
 mod cat;
 mod print_cfg;
 mod rsfilecheck;
@@ -19,6 +19,7 @@ const USAGE: &'static str = "
 Cretonne code generator utility
 
 Usage:
+    cton-util test <file>...
     cton-util cat <file>...
     cton-util filecheck [-v] <file>
     cton-util print-cfg <file>...
@@ -33,6 +34,7 @@ Options:
 
 #[derive(RustcDecodable, Debug)]
 struct Args {
+    cmd_test: bool,
     cmd_cat: bool,
     cmd_filecheck: bool,
     cmd_print_cfg: bool,
@@ -55,7 +57,9 @@ fn cton_util() -> CommandResult {
         .unwrap_or_else(|e| e.exit());
 
     // Find the sub-command to execute.
-    if args.cmd_cat {
+    if args.cmd_test {
+        filetest::run(args.arg_file)
+    } else if args.cmd_cat {
         cat::run(args.arg_file)
     } else if args.cmd_filecheck {
         rsfilecheck::run(args.arg_file, args.flag_verbose)