Move initialization into declaration when they're back-to-back

[bbrk24]

Bug report or Feature request?

Feature request

Version (complete output of terser -V or specific git commit)

terser 5.19.3

Complete CLI command or minify() options used

{
  module: false,
  compress: {},
  mangle: {},
  output: {},
  parse: {},
  rename: {},
}

That is, the default options for the online REPL but with module: false.

terser input

var x;
x = 1;

var y;
y = undefined;

terser output or error

var x,y;x=1,y=void 0;

Expected result

var x=1,y;