Updated the build process to formally declare that we're compiling from ES6 to ES5 (although for now, 99.99% of the code is already and will remain ES5.1-compatible)

Gruntfile.js

@@ -282,6 +282,8 @@ module.exports = function(grunt) {
                     externs: pkg.closureCompilerExterns,
                     define: ["'SITEHOST=\"www.pcjs.org\"'", "'COMPILED=true'", "'DEBUG=false'"],
                     warning_level: "verbose",
+                    language_in: "ES6",                 // this is now the default, just documenting our requirements
+                    language_out: "ES5",                // this is also the default
                     // jscomp_off: ["checkTypes", "fileoverviewTags"],
                     // summary_detail_level: 3,
                     // formatting: "PRETTY_PRINT --debug",

gulpfile.js

@@ -114,6 +114,8 @@ gulp.task('compile', function() {
             },
             externs: [{src: sExterns}],
             warningLevel: 'VERBOSE',
+            languageIn: "ES6",                          // this is now the default, just documenting our requirements
+            languageOut: "ES5",                         // this is also the default
             outputWrapper: '(function(){%output%})()',
             jsOutputFile: pcX86ReleaseFile,             // TODO: This must vary according to debugger/non-debugger releases
             createSourceMap: false