change relative priority of auto-slice and auto-ptr

rationale: if you have an impl for &const ~[T] or &mut ~[T]
and one for &[T], the first will be more likely to work and not lead
to borrowck errors.  I could imagine us wanting to offer multiple
impls for methods we select the ptr-to-array when possible and
the slice when necessary.  Also, taking a ptr seems like fewer
adaptations than slicing, and we tend to prefer fewer adaptations.

src/rustc/middle/typeck/check/method.rs

@@ -527,12 +527,12 @@ impl LookupContext {
          * Attempts both auto-slice and auto-ptr, as appropriate.
          */
 
-        match self.search_for_autosliced_method(self_ty, autoderefs) {
+        match self.search_for_autoptrd_method(self_ty, autoderefs) {
             Some(move mme) => { return Some(move mme); }
             None => {}
         }
 
-        match self.search_for_autoptrd_method(self_ty, autoderefs) {
+        match self.search_for_autosliced_method(self_ty, autoderefs) {
             Some(move mme) => { return Some(move mme); }
             None => {}
         }