Tests fixes and debug vector pendantic capacity management change

[François Dumont]

On 20/12/2014 19:09, Jonathan Wakely wrote:
>>    There are also 2 tests that XPASS:
>> XPASS: experimental/string_view/element_access/char/2.cc execution test
>> XPASS: experimental/string_view/element_access/wchar_t/2.cc execution 
>> test
>>
>>    Debug assertions has been commented about because not compatible 
>> with constexpr. Do we keep them this way ?
>
> Yes, otherwise they stop being constexpr.
>

I was more wondering if it fine to keep tests reporting a XPASS status 
cause they are displayed as the FAIL ones. But I think that XPASS is 
indeed a good status for a temporary issue.

Patch committed.

François