Make whitespace comparison better.

[ykmnkmi]

For example write char code (10, 13, ...) or literal (\n, \r, ...) at cursor position.

00:02 +28 -1: test/common/pipes/date_pipe_test.dart: DatePipe transform should format each component correctly [E]
  Expected: '9 PM'
    Actual: '9 PM'
     Which: is different.
            Expected: 9 PM
              Actual: 9 PM
                       ^
             Differ at offset 1
  
  package:matcher           expect$0
  date_pipe_test.dart 36:9  <fn>
  
00:02 +28 -1: test/common/pipes/date_pipe_test.dart: DatePipe transform should format common multi component patterns
00:02 +28 -2: test/common/pipes/date_pipe_test.dart: DatePipe transform should format common multi component patterns [E]
  Expected: '9:43:11 PM'
    Actual: '9:43:11 PM'
     Which: is different.
            Expected: 9:43:11 PM
              Actual: 9:43:11 PM
                             ^
             Differ at offset 7
  
  package:matcher           expect$0
  date_pipe_test.dart 45:9  <fn>
  
00:02 +28 -2: test/common/pipes/date_pipe_test.dart: DatePipe transform should format with pattern aliases
00:02 +28 -3: test/common/pipes/date_pipe_test.dart: DatePipe transform should format with pattern aliases [E]
  Expected: 'Jun 15, 2015, 9:43:11 PM'
    Actual: 'Jun 15, 2015, 9:43:11 PM'
     Which: is different.
            Expected: ... 5, 9:43:11 PM
              Actual: ... 5, 9:43:11 PM
                                    ^
             Differ at offset 21
  
  package:matcher           expect$0
  date_pipe_test.dart 49:9  <fn>
  
00:02 +28 -3: test/common/pipes/date_pipe_test.dart: DatePipe transform should format millis in local timezone
00:02 +28 -4: test/common/pipes/date_pipe_test.dart: DatePipe transform should format millis in local timezone [E]
  Expected: '9 PM'
    Actual: '9 PM'
     Which: is different.
            Expected: 9 PM
              Actual: 9 PM
                       ^
             Differ at offset 1
  
  package:matcher           expect$0
  date_pipe_test.dart 70:9  <fn>