oledb32: Support DBTYPE_NUMERIC in IDataConvert GetConversionSize.

dlls/oledb32/convert.c

@@ -139,6 +139,8 @@ static int get_length(DBTYPE type)
         return sizeof(FILETIME);
     case DBTYPE_GUID:
         return sizeof(GUID);
+    case DBTYPE_NUMERIC:
+        return sizeof(DB_NUMERIC);
     case DBTYPE_BYTES:
     case DBTYPE_WSTR:
     case DBTYPE_STR:

dlls/oledb32/tests/convert.c

@@ -2857,6 +2857,9 @@ static void test_getconversionsize(void)
     ok(hr == S_OK, "got 0x%08x\n", hr);
     VariantClear(&var);
 
+    hr = IDataConvert_GetConversionSize(convert, DBTYPE_NUMERIC, DBTYPE_NUMERIC, NULL, &dst_len, NULL);
+    ok(hr == S_OK, "got 0x%08x\n", hr);
+    ok(dst_len == sizeof(DB_NUMERIC), "%ld\n", dst_len);
 }
 
 static void test_converttobytes(void)