Change remaining "iface" occurrences to "trait"; deprecate "iface"

src/libsyntax/ext/base.rs

@@ -114,7 +114,7 @@ fn syntax_expander_table() -> hashmap<~str, syntax_extension> {
 // One of these is made during expansion and incrementally updated as we go;
 // when a macro expansion occurs, the resulting nodes have the backtrace()
 // -> expn_info of their expansion context stored into their span.
-iface ext_ctxt {
+trait ext_ctxt {
     fn codemap() -> codemap;
     fn parse_sess() -> parse::parse_sess;
     fn cfg() -> ast::crate_cfg;

src/libsyntax/ext/pipes/pipec.rs

@@ -383,7 +383,7 @@ impl compile of gen_init for protocol {
     }
 }
 
-iface to_source {
+trait to_source {
     // Takes a thing and generates a string containing rust code for it.
     fn to_source() -> ~str;
 }

src/libsyntax/ext/qquote.rs

@@ -22,7 +22,7 @@ enum fragment {
     from_ty(@ast::ty)
 }
 
-iface qq_helper {
+trait qq_helper {
     fn span() -> span;
     fn visit(aq_ctxt, vt<aq_ctxt>);
     fn extract_mac() -> option<ast::mac_>;