fix the "number of table" calculation for multi-record tables

It turns out that the empty-record detection worked fine, but that the
last empty record of a keyword is ignored by opm-parser for reasons
which are not clear to me...

Now all unit tests pass.

opm/parser/eclipse/Utility/MultiRecordTable.cpp

@@ -38,6 +38,10 @@ size_t MultiRecordTable::numTables(Opm::DeckKeywordConstPtr keyword)
             ++ result;
     }
 
+    // the last empty record of a keyword seems to go MIA for some
+    // strange reason...
+    ++result;
+
     return result;
 }