Avoids std::distance calls

[François Dumont]

Hi

I'd like to propose this patch to avoid std::distance calls. In a number 
of situation in algos we already have the size of the buffer we need so 
we shouldn't have to compute it again.

I don't think there is any abi concern for this inline constructor, 
isn't there ?

 Â Â Â  * include/bits/stl_tempbuf.h
 Â Â Â  (_Temporary_buffer(_FwdIte, _FwdIte)): Delete, replaced by...
 Â Â Â  (_Temporary_buffer(_FwdIte, size_type)): ...this, new.
 Â Â Â  * include/ext/memory (temporary_buffer<>(_FwdIte, _FwdIte)): Adapt.
 Â Â Â  * include/bits/stl_algo.h (__stable_partition): Adapt.
 Â Â Â  (__inplace_merge): Adapt.
 Â Â Â  (__stable_sort): Adapt.

Tested under Linux x86_64 normal mode.

Ok to commit ?

François

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