make the seed of a MersenneTwister be always a Vector{Uint32}

MersenneTwister's constructor making an instance with an Uint32 seed
was removed in commit 4fb4622f5c. But a subsequent call to
srand(r::MersenneTwister, seed) would only accept an Uint32 as a seed,
and would always make r.seed an Uint32; this was not consistent.
add more methods srand(::MersenneTwister, ...)

The srand methods working on a MersenneTwister instance did not catch
up with those working on the global RNG. They are now made similar
thanks to the make_seed function, which implements the different
logics.
Also, the manual is more precise on the types of valid seeds.
add more methods rand(rng, ...)

And similarly for rand!, randbool.
Fixes #8360.
Setting OPENBLAS_TARGET_ARCH should disable OPENBLAS_DYNAMIC_ARCH by default
add a test for getindex(::Number, ::Real)

ref b718cbc72e90
Merge pull request #8854 from JuliaLang/rf/rand-rng

RFC: more methods working with a non-global RNG
update helpdb.jl
In \, only estimate rank and use complete orthogonal factorization for pivoted qr factorizations.
Merge pull request #8860 from JuliaLang/sf/openblas_dynamic_arch

Setting OPENBLAS_TARGET_ARCH disables OPENBLAS_DYNAMIC_ARCH by default
Small integer powers are no longer slow.

This has been fixed in issue #2741.
Merge pull request #8878 from ntessore/nt/doc-perf

Updated manual: Small integer powers are no longer slow.
Adapt to LLVM3.6 API change
Modal prefix history search.

Attempt to deal with down arrow better at end of history.
Refine prefix matching condition to consider mode changes as different.
Exit prefix searching mode on ctrl+C.
No need to reset history provider when resetting PrefixHistoryPrompt.
Pass thru keypresses to parent mode.
Cleanup some mess with types in LineEdit.jl
Fix lineedit test failure.