Add verification flags to debug mjsunit test runs.

test/mjsunit/testcfg.py

Index: test/mjsunit/testcfg.py
===================================================================
--- test/mjsunit/testcfg.py	(revision 2809)
+++ test/mjsunit/testcfg.py	(working copy)
@@ -31,7 +31,7 @@
 import re
 import tempfile
 
-
+MJSUNIT_DEBUG_FLAGS = ['--enable-slow-asserts', '--debug-code', '--verify-heap']
 FLAGS_PATTERN = re.compile(r"//\s+Flags:(.*)")
 FILES_PATTERN = re.compile(r"//\s+Files:(.*)")
 SELF_SCRIPT_PATTERN = re.compile(r"//\s+Env: TEST_FILE_NAME")
@@ -58,6 +58,8 @@
     flags_match = FLAGS_PATTERN.search(source)
     if flags_match:
       result += flags_match.group(1).strip().split()
+    if self.mode == 'debug':
+      result += MJSUNIT_DEBUG_FLAGS
     additional_files = []
     files_match = FILES_PATTERN.search(source);
     # Accept several lines of 'Files:'