add PS4 and SHELLOPTS to initial_badenv_table for bash

env.c

@@ -142,6 +142,8 @@ static const char *initial_badenv_table[] = {
     "TERMCAP",			/* XXX - only if it starts with '/' */
     "ENV",
     "BASH_ENV",
+    "PS4",
+    "SHELLOPTS",
     NULL
 };