New file msvcrt/excpt.h. Move some stuff out of winnt.h into it.

memory/string.c

diff --git a/memory/string.c b/memory/string.c
index caa994a..b2ac9e1 100644
--- a/memory/string.c
+++ b/memory/string.c
@@ -15,6 +15,7 @@
 #include "wine/unicode.h"
 #include "winerror.h"
 #include "winnls.h"
+#include "msvcrt/excpt.h"
 #include "debugtools.h"
 
 DEFAULT_DEBUG_CHANNEL(string);