Fix Error.prototype.toString to be ES5 conform.

test/test262/test262.status

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@@ skipping 484 matching lines @@
 15.9.5.43-0-12: FAIL
 # Bug? Date.prototype.toISOString - RangeError is thrown when value of date is
 #      Date(1970, 0, 100000001, 0, 0, 0, 1), the time zone is UTC(0)
 15.9.5.43-0-13: FAIL
 # Bug? Date.prototype.toISOString - when value of year is -Infinity
 #      Date.prototype.toISOString throw the RangeError
 15.9.5.43-0-14: FAIL
 # Bug? Date.prototype.toISOString - value of year is Infinity
 #      Date.prototype.toISOString throw the RangeError
 15.9.5.43-0-15: FAIL
-# Bug? Error.prototype.toString return the value of 'msg' when 'name' is empty
-#      string and 'msg' isn't undefined
-15.11.4.4-8-1: FAIL
 
 ############################ SKIPPED TESTS #############################
 
 # These tests take a looong time to run in debug mode.
 S15.1.3.2_A2.5_T1: PASS, SKIP if $mode == debug
 S15.1.3.1_A2.5_T1: PASS, SKIP if $mode == debug
 
 [ $arch == arm ]
 
 # BUG(3251225): Tests that timeout with --nocrankshaft.
 S15.1.3.1_A2.5_T1: SKIP
 S15.1.3.2_A2.5_T1: SKIP
 S15.1.3.1_A2.4_T1: SKIP
 S15.1.3.1_A2.5_T1: SKIP
 S15.1.3.2_A2.4_T1: SKIP
 S15.1.3.2_A2.5_T1: SKIP
 S15.1.3.3_A2.3_T1: SKIP
 S15.1.3.4_A2.3_T1: SKIP
 S15.1.3.1_A2.5_T1: SKIP
 S15.1.3.2_A2.5_T1: SKIP
 
 [ $arch == mips ]
 
 # Skip all tests on MIPS.
 *: SKIP