Format the function name and file-position into proper columns to easily spot
where the test code ends and the mjsunit framework code starts.

BEFORE:
Stack: Error
    at new MjsUnitAssertionError (test/mjsunit/mjsunit.js:36:18)
    at failWithMessage (test/mjsunit/mjsunit.js:310:11)
    at fail (test/mjsunit/mjsunit.js:327:12)
    at assertEquals (test/mjsunit/mjsunit.js:398:7)
    at closure (test/mjsunit/regress/regress-4121.js:20:7)
    at literals_sharing_test (test/mjsunit/regress/regress-4121.js:27:3)
    at test (test/mjsunit/regress/regress-4121.js:37:5)
    at eval (eval at <anonymous> (test/mjsunit/regress/regress-4121.js:49:6), <anonymous>:1:1)
    at test/mjsunit/regress/regress-4121.js:49:6
    at Array.forEach.call (test/mjsunit/regress/regress-4121.js:50:7)
    throw new MjsUnitAssertionError(message);

AFTER:
Stack: MjsUnitAssertionError
    at assertEquals          test/mjsunit/mjsunit.js 398:7
    at closure               test/mjsunit/regress/regress-4121.js 20:7
    at literals_sharing_test test/mjsunit/regress/regress-4121.js 27:3
    at test                  test/mjsunit/regress/regress-4121.js 37:5
    at eval                  eval at <anonymous> (test/mjsunit/regress/regress-4121.js:49:6)
    at                       test/mjsunit/regress/regress-4121.js 49:6
    at Array.forEach.call    test/mjsunit/regress/regress-4121.js 50:7
    throw new MjsUnitAssertionError(message);


Change-Id: Iad3460a648e26effb43c00426ab043743ee6a138
Reviewed-on: https://chromium-review.googlesource.com/563627Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46589}