Fix Debug DR2354

[François Dumont]

Now backported to branch.


On 24/12/2017 08:55, Jonathan Wakely wrote:
> On 19 December 2017 at 21:33, François Dumont wrote:
>> Hi
>>
>>    I plan to apply attached patch tomorrow to fix those _GLIBCXX_DEBUG
>> failures:
>>
>> FAIL: 23_containers/map/modifiers/insert/dr2354.cc (test for excess errors)
>> FAIL: 23_containers/multimap/modifiers/insert/dr2354.cc (test for excess
>> errors)
>> FAIL: 23_containers/unordered_map/insert/dr2354.cc (test for excess errors)
>> FAIL: 23_containers/unordered_multimap/insert/dr2354.cc (test for excess
>> errors)
>>
>>    I am also adding tests checking additional DR 2354 insert overloads. I
>> discovered I needed to add those only because I looked at the ChangeLog
>> entry.
>>
>>    Tested under Linux x86_64 Debug mode.
> Thanks, this also needs to be fixed on gcc-7-branch.
>