gh-95778: add doc missing in some places (GH-100627)

Misc/python.man

@@ -358,6 +358,10 @@ Set implementation-specific option. The following options are available:
     -X frozen_modules=[on|off]: whether or not frozen modules should be used.
        The default is "on" (or "off" if you are running a local build).
 
+    -X int_max_str_digits=number: limit the size of int<->str conversions.
+       This helps avoid denial of service attacks when parsing untrusted data.
+       The default is sys.int_info.default_max_str_digits.  0 disables.
+
 .TP
 .B \-x
 Skip the first line of the source.  This is intended for a DOS
@@ -531,6 +535,11 @@ values.
 
 The integer must be a decimal number in the range [0,4294967295].  Specifying
 the value 0 will disable hash randomization.
+.IP PYTHONINTMAXSTRDIGITS
+Limit the maximum digit characters in an int value
+when converting from a string and when converting an int back to a str.
+A value of 0 disables the limit.  Conversions to or from bases 2, 4, 8,
+16, and 32 are never limited.
 .IP PYTHONMALLOC
 Set the Python memory allocators and/or install debug hooks. The available
 memory allocators are

Python/initconfig.c

@@ -180,6 +180,8 @@ static const char usage_envvars[] =
 "PYTHONDEBUG             : enable parser debug mode (-d)\n"
 "PYTHONDONTWRITEBYTECODE : don't write .pyc files (-B)\n"
 "PYTHONINSPECT           : inspect interactively after running script (-i)\n"
+"PYTHONINTMAXSTRDIGITS   : limit max digit characters in an int value\n"
+"                          (-X int_max_str_digits=number)\n"
 "PYTHONNOUSERSITE        : disable user site directory (-s)\n"
 "PYTHONOPTIMIZE          : enable level 1 optimizations (-O)\n"
 "PYTHONUNBUFFERED        : disable stdout/stderr buffering (-u)\n"