Merge pull request microsoft#9006 from Microsoft/transforms-removeLegacyEmitter

[Transforms] Replace legacy emitter with tree transforming emitter.

Author: rbuckton

Jakefile.js

@@ -374,12 +374,6 @@ namespace ts {
             type: "boolean",
             description: Diagnostics.Do_not_emit_use_strict_directives_in_module_output
         },
-        {
-            name: "useLegacyEmitter",
-            type: "boolean",
-            experimental: true,
-            description: Diagnostics.Use_the_legacy_emitter_instead_of_the_transforming_emitter
-        },
         {
             name: "listEmittedFiles",
             type: "boolean"

src/compiler/commandLineParser.ts

@@ -2773,10 +2773,6 @@
         "code": 6131
     },
 
-    "Use the legacy emitter instead of the transforming emitter.": {
-        "category": "Message",
-        "code": 6132
-    },
     "Variable '{0}' implicitly has an '{1}' type.": {
         "category": "Error",
         "code": 7005