include: Fix error logic

[André Hentschel]

The file is nearly always used with one of both, so "or" makes no sense.
Also if you have a look through tchar.h you see it catches all cases,
but not the case where both are defined
---
 include/tchar.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/tchar.h b/include/tchar.h
index 38885d4..497e0aa 100644
--- a/include/tchar.h
+++ b/include/tchar.h
@@ -23,7 +23,7 @@
 #error Wine should not include tchar.h internally
 #endif
 
-#if defined(_UNICODE) || defined(_MBCS)
+#if defined(_UNICODE) && defined(_MBCS)
 #error You must use msvcrt when building in Unicode/MBCS mode
 #endif
 
-- 

Best Regards, André Hentschel