bpo-34228: Allow PYTHONTRACEMALLOC=0 (GH-8467)

PYTHONTRACEMALLOC=0 environment variable and -X tracemalloc=0 command
line option are now allowed to disable explicitly tracemalloc at
startup.
diff --git a/Include/pystate.h b/Include/pystate.h
index fe14832..2c70505 100644
--- a/Include/pystate.h
+++ b/Include/pystate.h
@@ -232,6 +232,7 @@
         .install_signal_handlers = -1, \
         .ignore_environment = -1, \
         .use_hash_seed = -1, \
+        .tracemalloc = -1, \
         .coerce_c_locale = -1, \
         .utf8_mode = -1, \
         .argc = -1, \