feat: add bytes.indexOf, server.acceptBatch, server.pendingCount, stdin data callback, and coverage/valgrind make targets

Implement `bytesIndexOf` foreign function supporting optional start offset for searching byte sequences. Add `serverAcceptBatch` and `serverPendingCount` to net module for batch accepting connections and querying pending queue size. Refactor `stdinFileTimerCallback` to pass read bytes to Wren callback instead of null, with separate handling for EOF. Introduce `coverage_64bit` build config with gcov flags, plus `coverage`, `valgrind`, `clean-coverage`, and `publish` phony targets in Makefile. Fix memory leak in regex by nullifying freed pointers on allocation failure.

util/test.py

@@ -27,6 +27,8 @@ parser.add_argument('--suffix', default='')
 parser.add_argument('suite', nargs='?')
 parser.add_argument('--skip-tests', action='store_true')
 parser.add_argument('--skip-examples', action='store_true')
+parser.add_argument('--valgrind', action='store_true',
+                    help='Run tests under valgrind')
 
 
 args = parser.parse_args(sys.argv[1:])
@@ -150,10 +152,15 @@ class Test:
     return True
 
 
-  def run(self, app, type):
-    # Invoke wren and run the test.
+  def run(self, app, type, valgrind=False):
     test_arg = self.path
-    proc = Popen([app, test_arg], stdin=PIPE, stdout=PIPE, stderr=PIPE)
+    if valgrind:
+      cmd = ['valgrind', '--leak-check=full', '--error-exitcode=99',
+             '--suppressions=' + join(dirname(realpath(__file__)), 'valgrind.supp'),
+             app, test_arg]
+    else:
+      cmd = [app, test_arg]
+    proc = Popen(cmd, stdin=PIPE, stdout=PIPE, stderr=PIPE)
 
     # If a test takes longer than five seconds, kill it.
     #
@@ -173,12 +180,14 @@ class Test:
       if timed_out[0]:
         self.fail("Timed out.")
       else:
-        self.validate(type == "example", proc.returncode, out, err)
+        if valgrind and proc.returncode == 99:
+          self.fail("Valgrind detected memory errors")
+        self.validate(type == "example", proc.returncode, out, err, valgrind)
     finally:
       timer.cancel()
 
 
-  def validate(self, is_example, exit_code, out, err):
+  def validate(self, is_example, exit_code, out, err, valgrind=False):
     if self.compile_errors and self.runtime_error_message:
       self.fail("Test error: Cannot expect both compile and runtime errors.")
       return
@@ -189,6 +198,13 @@ class Test:
     except:
       self.fail('Error decoding output.')
 
+    if valgrind:
+      err_lines = []
+      for line in err.split('\n'):
+        if not line.startswith('==') and not line.startswith('--'):
+          err_lines.append(line)
+      err = '\n'.join(err_lines)
+
     error_lines = err.split('\n')
 
     # Validate that an expected runtime error occurred.
@@ -376,7 +392,7 @@ def run_script(app, path, type):
     # It's a skipped or non-test file.
     return
 
-  test.run(app, type)
+  test.run(app, type, args.valgrind)
 
   # Display the results.
   if len(test.failures) == 0: