Discard first line of multiline string if only whitespace

tests/co19/co19-runtime.status

Index: tests/co19/co19-runtime.status
===================================================================
--- tests/co19/co19-runtime.status	(revision 27888)
+++ tests/co19/co19-runtime.status	(working copy)
@@ -72,7 +72,6 @@
 Language/07_Classes/6_Constructors/1_Generative_Constructors_A09_t01: fail # Dart issue 12543
 Language/12_Expressions/05_Strings_A02_t46: fail # Dart issue 12547
 Language/12_Expressions/05_Strings_A02_t48: fail # Dart issue 12547
-Language/12_Expressions/05_Strings_A20_t01: fail # Dart issue 12518
 Language/12_Expressions/12_Instance_Creation/1_New_A06_t12: fail # Dart issue 12549
 Language/12_Expressions/12_Instance_Creation/1_New_A09_t09: fail # Dart issue 1372
 Language/12_Expressions/12_Instance_Creation/2_Const_A10_t01: fail # co19 issue 525
@@ -97,13 +96,10 @@
 Language/14_Libraries_and_Scripts/2_Exports_A04_t02: fail # Dart issue 12916
 Language/14_Libraries_and_Scripts/2_Exports_A04_t03: fail # Dart issue 12916
 Language/14_Libraries_and_Scripts/2_Exports_A05_t01: fail # Dart issue 12918
-Language/14_Libraries_and_Scripts/5_URIs_A01_t01: fail # Issue 12521
 Language/14_Libraries_and_Scripts/5_URIs_A01_t04: fail # Issue 12521
 Language/14_Libraries_and_Scripts/5_URIs_A01_t05: fail # Issue 12521
-Language/14_Libraries_and_Scripts/5_URIs_A01_t11: fail # Issue 12521
 Language/14_Libraries_and_Scripts/5_URIs_A01_t14: fail # Issue 12521
 Language/14_Libraries_and_Scripts/5_URIs_A01_t15: fail # Issue 12521
-Language/14_Libraries_and_Scripts/5_URIs_A01_t21: fail # Issue 12518
 
 LibTest/core/DateTime/parse_A03_t01: fail # Issue 12514