Add support for \b and ^ and $ in multiline mode, completing Irregexp...

src/interpreter-irregexp.cc

 // Copyright 2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 472 matching lines @@
         } else {
           if (BackRefMatchesNoCase(from, current, len, subject)) {
             current += len;
             pc += BC_CHECK_NOT_BACK_REF_NO_CASE_LENGTH;
           } else {
             pc = code_base + Load32(pc + 2);
           }
         }
         break;
       }
+      BYTECODE(CHECK_AT_START)
+        if (current == 0) {
+          pc = code_base + Load32(pc + 1);
+        } else {
+          pc += BC_CHECK_AT_START_LENGTH;
+        }
+        break;
       BYTECODE(CHECK_NOT_AT_START)
         if (current == 0) {
           pc += BC_CHECK_NOT_AT_START_LENGTH;
         } else {
           pc = code_base + Load32(pc + 1);
         }
         break;
       default:
         UNREACHABLE();
         break;
@@ skipping 25 matching lines @@
     if (start_position != 0) previous_char = subject_vector[start_position - 1];
     return RawMatch(code_base,
                     subject_vector,
                     registers,
                     start_position,
                     previous_char);
   }
 }
 
 } }  // namespace v8::internal