Silence g++-7.4 warning (Ubuntu 18)

Which is a wrong warning, which came with LTO and -O3.
Newer g++ can detect that it is initialized in this branch

Author: rurban

src/util/format_number_range.cpp

@@ -73,6 +73,11 @@ std::string format_number_range(const std::vector<unsigned> &input_numbers)
 }
 
 /// Appends \p number resp. numbers \p begin_range ... \p number to \p numbers
+/// Old g++ with -O3 falsely complain for *begin_range (g++-7.4)
+#if __GNUC__ > 4
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wuninitialized"
+#endif
 static void append_numbers_and_reset(
   const std::string &number_range,
   std::vector<unsigned> &numbers,
@@ -113,6 +118,9 @@ static void append_numbers_and_reset(
     number = {};
   }
 }
+#if __GNUC__ > 4
+#  pragma GCC diagnostic pop
+#endif
 
 std::vector<unsigned> parse_number_range(const std::string &number_range)
 {