allow ascii_only flag on compression

bin/uglifyjs

@@ -225,6 +225,9 @@ if (ARGS.keep_fnames) {
 if (BEAUTIFY)
     UglifyJS.merge(OUTPUT_OPTIONS, BEAUTIFY);
 
+if (COMPRESS)
+    OUTPUT_OPTIONS.ascii_only = !!COMPRESS.ascii_only
+
 if (ARGS.comments != null) {
     if (/^\/.*\/[a-zA-Z]*$/.test(ARGS.comments)) {
         try {

lib/compress.js

@@ -74,6 +74,7 @@ function Compressor(options, false_by_default) {
         screw_ie8     : false,
         drop_console  : false,
         angular       : false,
+        ascii_only    : false,
 
         warnings      : true,
         global_defs   : {}

test/compress/ascii_only.js

@@ -0,0 +1,19 @@
+prevents_unicode_escape_sequences_from_being_converted: {
+    options = {ascii_only: true};
+    input: {
+        var a = "\u2000";
+    }
+    expect: {
+        var a = "\u2000";
+    }
+}
+
+converts_unicode_characters_to_escape_sequences: {
+    options = {ascii_only: true};
+    input: {
+        var a = " ";
+    }
+    expect: {
+        var a = "\u2000";
+    }
+}