reimplement some of the unsafe stuff which got lost

- blocks inherit unsafety
  - remove the --check-unsafe flag
  - add unsafe annotations where needed to get things to compile

src/comp/driver/rustc.rs

@@ -325,7 +325,6 @@ fn build_session_options(match: getopts::match)
 
     let parse_only = opt_present(match, "parse-only");
     let no_trans = opt_present(match, "no-trans");
-    let check_unsafe = opt_present(match, "check-unsafe");
 
     let output_type =
         if parse_only || no_trans {
@@ -397,8 +396,7 @@ fn build_session_options(match: getopts::match)
           parse_only: parse_only,
           no_trans: no_trans,
           do_gc: do_gc,
-          stack_growth: stack_growth,
-          check_unsafe: check_unsafe};
+          stack_growth: stack_growth};
     ret sopts;
 }
 

src/comp/driver/session.rs

@@ -41,8 +41,7 @@ type options =
      parse_only: bool,
      no_trans: bool,
      do_gc: bool,
-     stack_growth: bool,
-     check_unsafe: bool};
+     stack_growth: bool};
 
 type crate_metadata = {name: str, data: [u8]};