Writes to TTYs are process blocking anyway, so no need to make them task-blocking
pkg2/resolve: add prerelase/build in VersionWeigth

this will allow to remove filtering of prerelease/build versions,
and "normalization" of packages requirements which was introduced
in 0fa84ec69f060cc492772b1a1707eff3745675bf
pkg2: reinstate prerelease/build versions

Prerelease/build versions can again be used in "require" files.

This essentially reverts commits
0fa84ec69f060cc492772b1a1707eff3745675bf
923e385d029b22df67739f7f1de6df18721d2f97
pkg2: more tests in resolve2

For the new weighting scheme. Also, sanitize previous
tetst a little.
AsyncStream => TTY is TTY-overwrite methods
Add documentation for conv2()/plan_brfft()
Added doc/UNDOCUMENTED.rst, functions for generating

This collects all known undocumented modules and functions and
puts them in doc/UNDOCUMENTED.rst, using standard function and
method templates so they can be easily filled in and copied to
the correct .rst file in doc/stdlib.

This file can be regenerated with

```julia
cd("$JULIA_HOME/../../doc")
import DocCheck
DocCheck.gen_undocumented_template()
```
expand the contexts that are considered "top level". fixes #3905

top level context now extends within begin blocks, if statements, etc.
as long as no new variable scopes are introduced. this allows conditional
"using" statements and so on at the top level, so we don't need usingmodule().

of course, introducing new variables can implicitly wrap expressions so
they become non-top-level. for example:

    # top level
    begin
        s = 0
        using Foo
    end

    # NOT top level
    begin
        local s = 0
        using Foo  # error
    end
Merge branch 'master' of github.com:JuliaLang/julia
small fix to serialize() to allow remote calling e.g. Core.eval
Merge branch 'master' of github.com:JuliaLang/julia
Merge pull request #3910 from JuliaLang/kf/synctty

TTY synchronous writes
fix #3909
Merge pull request #3912 from kmsquire/undocumented_updates

Added doc/UNDOCUMENTED.rst, functions for generating
Merge pull request #3913 from JuliaLang/sf/dspdocs

Add documentation for conv2()/plan_brfft()
base/Makefile: fix FreeBSD date bug; replace $(CC -E) -> $(CPP)
Update openblas to v0.2.8-rc1 for wider testing.
bump openblas from v0.2.8-rc1 -> v0.2.8
Remove deprecated addprocs_sge entry. The documentation did say
that the function was deprecated, but we are not doing this elsewhere -
hence deleting this entry.
Updated package list, now with 200 packages