Update to clang-format-5 and reformat the codebase 

This includes dragging the libcxx implementation of normal_distribution
and uniform_int_distribution into our source. MSVC, clang and gcc don't
agree on how this should be implemented leading to problems with
comparing test results across platforms. Using a single implementation
gives the same results on each platform.

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Merge done to enable documentation be be fixed, because of removal of
alias directive and addition of related algorithms directive.

Signed-off-by: Karl Palmen <karl.palmen@stfc.ac.uk>

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Signed-off-by: Karl Palmen <karl.palmen@stfc.ac.uk>