patch #1668: clarify envvar docs; rename THREADDEBUG to PYTHONTHREADDEBUG.
diff --git a/Modules/main.c b/Modules/main.c
index 71c9c59..3d4b9be 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -62,7 +62,7 @@
-B : don't write .py[co] files on import; also PYTHONDONTWRITEBYTECODE=x\n\
-c cmd : program passed in as string (terminates option list)\n\
-d : debug output from parser; also PYTHONDEBUG=x\n\
--E : ignore environment variables (such as PYTHONPATH)\n\
+-E : ignore PYTHON* environment variables (such as PYTHONPATH)\n\
-h : print this help message and exit (also --help)\n\
-i : inspect interactively after running script; forces a prompt even\n\
";