'random' test fails on master

[nalimilan]

The random test fails on the RPM nightlies on Fedora 20 and RHEL7. Unfortunately I don't know when the failure was introduced since the build was failing for unrelated reasons for a few days. At least it was passing on 2014-10-18. I can do some bisection if that's useful.

/builddir/build/BUILD/julia/build/usr/bin/julia --check-bounds=yes -f ./runtests.jl random
     �[1m*�[0m �[31mrandom�[0m
exception on 1: ERROR: test error in expression: rand(MersenneTwister(0),1) == [0.8236475079774124]
`rand` has no method matching rand(::MersenneTwister, ::Type{Float64})
while loading random.jl, in expression starting on line 23
ERROR: test error in expression: rand(MersenneTwister(0),1) == [0.8236475079774124]
`rand` has no method matching rand(::MersenneTwister, ::Type{Float64})
while loading random.jl, in expression starting on line 23
while loading /builddir/build/BUILD/julia/test/runtests.jl, in expression starting on line 40
make: *** [random] Error 1

[rfourquet]

I think it was introduced in 89befaf. I'm up to fix this as part of #8380.

[rfourquet]

It turns out that the random tests pass again with #8832 (where a specialization for MersenneTwister of rand! was added).

[nalimilan]

Closed by #8399.