config.h: fix incorrect defines for _wopen()

This is a regression from commit

  0134184 ("add basic CMake based build")

S_IRUSR and S_IWUSR should NOT be defined as 0 but
as _S_IREAD and _S_IWRITE, as it was already fixed in commit

  077445d ("Fix some more wrong defines in config-msvc.h")

Those are used as permission mode when opening a file. Passing
zero makes file read-only, which break for example --status-file
functionality.

Github: fixes OpenVPN/openvpn#454
Trac: #1430

Change-Id: I53eaee85d7b284af6bc63da5f6d8f310ddd96c47
Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20231114141653.10486-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg27393.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>

config.h.cmake.in

@@ -469,8 +469,8 @@ typedef SSIZE_T ssize_t;
 #define strncasecmp strnicmp
 #define strcasecmp _stricmp
 
-#define S_IRUSR 0
-#define S_IWUSR 0
+#define S_IRUSR _S_IREAD
+#define S_IWUSR _S_IWRITE
 #define R_OK 4
 #define W_OK 2
 #define X_OK 1