Support host count in machinefile

- Support the syntax `[user@]host[:port][*count] [bind_addr]` in the
  machinefile.
- Initial code just re-writes the list fed to addprocs() by repeating the host
  as specified, so there is no user-visible change.
Move the host count to the beginning: [count*]...
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.
Move clear_malloc_data into Profile and add more documentation
Merge branch 'machinefile_count' of git://github.com/wavexx/julia into wavexx-machinefile_count

Conflicts:
	base/client.jl
	doc/manual/getting-started.rst
Merge pull request #8863 from amitmurthy/wavexx-machinefile_count

Wavexx machinefile count
Delete redundant export
fix #8865, comprehension evaluated in wrong module

this was because the REPL task was still "in" the old Main
module, and `expand` depends on the current module but doesn't take
a module argument. fortunately there doesn't seem to be any need to
call `expand` explicitly here.
Merge branch 'master' of github.com:JuliaLang/julia
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