[tobil4sk]

This already works on most targets. For example, php already has special handling for this case:

haxe/std/php/_std/Type.hx

Lines 136 to 137 in e592de2

	if (String == cast cl)
	return cast '';

Without this, there are failures like:

unit.teststd.TestType
  test: ERROR ............................E
    bin/unit.lua:108302: attempt to concatenate a table value

unit.teststd.TestType
  test: ERROR ............................E
    std@string_split
Called from String::split line 107
Called from StringTools::replace line 405
Called from unit.Test::eq line 19
Called from unit.teststd.TestType::test line 71
Called from unit.teststd.TestType::__initializeUtest__ line 4

unit.teststd.TestType
  test: ERROR ............................E
    String.prototype.valueOf requires that 'this' be a String
Called from module TypeError: String.prototype.valueOf requires that 'this' be a String
Called from module at String.valueOf (<anonymous>)
Called from utest_Assert.equals (/.../haxe/tests/unit/bin/unit.js line 76090 column 22)
Called from unit_teststd_TestType.eq (/.../haxe/haxe/tests/unit/bin/unit.js line 11790 column 16)
Called from unit_teststd_TestType.test (/.../haxe/tests/unit/bin/unit.js line 72248 column 8)
Called from Object.execute (/.../haxe/tests/unit/bin/unit.js line 72354 column 11)
Called from utest_TestHandler.runTest (/.../haxe/tests/unit/bin/unit.js line 77149 column 31)
Called from utest_TestHandler.checkSetup (/.../haxe/tests/unit/bin/unit.js line 77144 column 9)
Called from utest_Async.then (/.../haxe/tests/unit/bin/unit.js line 76677 column 4)
Called from utest_TestHandler.runSetup (/.../haxe/tests/unit/bin/unit.js line 77137 column 19)
Called from utest_TestHandler.execute (/.../haxe/tests/unit/bin/unit.js line 77116 column 8)