[CodeCompletion] Remove incorrect special-casing for throw/catch

It's not okay to filter to only ErrorType results, since we may be
trying to chain to an error type result foo.bar.getError().  And the
existing logic had no way to handle results from other modules, so we
were missing key results like 'NSError'.

Eventually we'll want to bring back something like this that handles all
modules, but as a way to bump the priority of ErrorType results rather
than to filter out everything else.

rdar://problem/20985515

Swift SVN r28716

include/swift/Parse/CodeCompletionCallbacks.h

@@ -130,12 +130,6 @@ public:
   /// \brief Complete a case stmt pattern that starts with a dot.
   virtual void completeCaseStmtDotPrefix() = 0;
 
-  /// \brief Complete at the beginning of a catch stmt pattern.
-  virtual void completeCatchStmtBeginning() = 0;
-
-  /// \brief Complete at the beginning of a throw stmt pattern.
-  virtual void completeThrowStmtBeginning() = 0;
-
   /// Complete at the beginning of member of a nominal decl member -- no tokens
   /// provided by user.
   virtual void completeNominalMemberBeginning(