cmAlgorithms: Implement algorithm for removing indexes.

Implement ContainerAlgorithms::RemoveN to remove N elements to the
end of a container by rotating.  The rotate is implemented in terms
of the efficient swap algorithm, optimized even more in the standard
library implementation when the compiler supports the rvalue-references
feature to move elements.  Implement cmRemoveN with a Range API
for completeness.

std::rotate in C++11 is specified to return an iterator, but
c++98 specifies it to return void.  libstdc++ 5.0 will be the first
version to have the correct return type.  Implement
ContainerAlgorithms::Rotate in terms of std::rotate and return the
correct iterator from it.  While std::rotate requires forward iterators,
 this workaround means cmRotate requires bidirectional iterators.  As
most of CMake uses random access iterators anyway, this should not
be a problem.

Implement cmRemoveIndices in terms of the RemoveN algorithm, such
that each element which is not removed is rotated only once.  This
can not use the cmRemoveN range-API algorithm because that would
require creating a new range, but the range must be taken by reference
and so it can't be a temporary.

These remove algorithms are not part of the STL and I couldn't find them
anywhere else either.

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