Merging predicated and non-predicated algorithms

[Paolo Carlini]

caj wrote:

> This patch changes equal, mismatch and lexicographical_compare in 
> stl_algobase.h and also provides tests for all 3 of them.

Ok, Chris, I like this version. If nobody objects, I will commit it to 
the v7 branch when I will be back from my vacations, on sunday or monday 
at most (this week, probably I have time only to fix the bug mentioned 
to Gaby)

Thanks again!
Paolo.