Fix #10758 Add compiler option to parse in strict mode

* add compiler option alwaysStrict
 * compile in strict mode when option is set
 * emit "use strict"

src/compiler/commandLineParser.ts

@@ -444,6 +444,11 @@ namespace ts {
             name: "importHelpers",
             type: "boolean",
             description: Diagnostics.Import_emit_helpers_from_tslib
+        },
+        {
+            name: "alwaysStrict",
+            type: "boolean",
+            description: Diagnostics.Parse_in_strict_mode_and_emit_use_strict_for_each_source_file
         }
     ];