Patch #552812: Better description in "python -h" for -u.

Misc/python.man

@@ -138,7 +138,11 @@ indentation in a way that makes it depend on the worth of a tab
 expressed in spaces.  Issue an error when the option is given twice.
 .TP
 .B \-u
-Force stdin, stdout and stderr to be totally unbuffered.
+Force stdin, stdout and stderr to be totally unbuffered.  Note that
+there is internal buffering in xreadlines(), readlines() and file-object
+iterators ("for line in sys.stdin") which is not influenced by this
+option.  To work around this, you will want to use "sys.stdin.readline()"
+inside a "while 1:" loop.
 .TP
 .B \-v
 Print a message each time a module is initialized, showing the place

Modules/main.c

@@ -62,6 +62,7 @@ static char *usage_2 = "\
 -S     : don't imply 'import site' on initialization\n\
 -t     : issue warnings about inconsistent tab usage (-tt: issue errors)\n\
 -u     : unbuffered binary stdout and stderr (also PYTHONUNBUFFERED=x)\n\
+         see man page for details on internal buffering relating to "-u"\n\
 ";
 static char *usage_3 = "\
 -v     : verbose (trace import statements) (also PYTHONVERBOSE=x)\n\