roken: do not globally define 'timezone' and 'tzname'

ec866e635e
("Windows 10 SDK build fixes") introduced CPP macros

  timezone -> _timezone
  tzname   -> _tzname

but these names are common and the macros rewrite too much.

The name mapping is only required when building strftime.c
with Visual Studio 2017 and later.  Move the definitions
into strftime.c.

Change-Id: Ic813bff842124595fd3d86761cee6dcea4ae44e4

lib/roken/roken.h.in

@@ -356,10 +356,6 @@ ROKEN_CPP_START
 
 #define fsync   _commit
 
-#define timezone    _timezone
-
-#define tzname  _tzname
-
 #define _PIPE_BUFFER_SZ 8192
 #define pipe(fds) _pipe((fds), _PIPE_BUFFER_SZ, O_BINARY);
 

lib/roken/strftime.c

@@ -36,6 +36,11 @@
 #include "strpftime-test.h"
 #endif
 
+#if defined(_WIN32)
+# define timezone _timezone
+# define tzname   _tzname
+#endif
+
 static const char *abb_weekdays[] = {
     "Sun",
     "Mon",