Port angle-bracket TZ settings to MS-Windows

* doc/lispref/os.texi (Time Zone Rules): Document MS-Windows
lack of support for numeric time zone abbreviations.
* src/w32.c (sys_putenv): Convert angle-bracket TZ syntax
to MS-compatible syntax if possible, and to "ZZZ" otherwise.
Problem reported by Kazuhiro Ito (Bug#23600).

1 files changed, 2 insertions, 1 deletions

diff --git a/doc/lispref/os.texi b/doc/lispref/os.texi
index becb691581b..38dde26d03a 100644
--- a/doc/lispref/os.texi
+++ b/doc/lispref/os.texi
@@ -1327,7 +1327,8 @@ If it is @code{t}, the conversion uses Universal Time.  If it is
 a string, the conversion uses the time zone rule equivalent to setting
 @env{TZ} to that string.  If it is an integer @var{offset}, the
 conversion uses a fixed time zone with the given offset and a numeric
-abbreviation.  If it is a list (@var{offset} @var{abbr}), where
+abbreviation on POSIX-compatible platforms and an unspecified abbreviation
+on MS-Windows.  If it is a list (@var{offset} @var{abbr}), where
 @var{offset} is an integer number of seconds east of Universal Time
 and @var{abbr} is a string, the conversion uses a fixed time zone with
 the given offset and abbreviation.