Added the {HRESULT,SCODE}_SEVERITY macros.

diff --git a/include/winerror.h b/include/winerror.h
index 52bed2c..40240b1 100644
--- a/include/winerror.h
+++ b/include/winerror.h
@@ -32,6 +32,9 @@
 #define HRESULT_FACILITY(hr)  (((hr) >> 16) & 0x1FFF)
 #define SCODE_FACILITY(sc)  (((sc) >> 16) & 0x1FFF)
 
+#define HRESULT_SEVERITY(hr)    (((hr) >> 31) & 0x1)
+#define SCODE_SEVERITY(sc)      (((sc) >> 31) & 0x1)
+
 #define FACILITY_NT_BIT         0x10000000
 #define HRESULT_FROM_WIN32(x)   ((x) ? ((HRESULT) (((x) & 0x0000FFFF) | (FACILITY_WIN32 << 16) | 0x80000000)) : 0 )
 #define HRESULT_FROM_NT(x)      ((HRESULT) ((x) | FACILITY_NT_BIT))