Add level1 and level2 BLAS performance tests.
Merge pull request #3727 from blakejohnson/blas-perf

Add level1 and level2 BLAS performance tests.
fix #3725
Merge branch 'master' of github.com:JuliaLang/julia
Set TK_LIBRARY to be able to use the system Tk library on OS X.
move DISABLE_FLOAT16 to the top of codegen; some uses were not seeing it
Merge branch 'master' of github.com:JuliaLang/julia
No longer copy the Tk libraries as part of the mac dmg.
Merge branch 'master' of github.com:JuliaLang/julia
fix #3729
Merge branch 'master' of github.com:JuliaLang/julia
Renasme uv_isopen -> isopen
Add callback for write
Make writes task-blocking by default
Actually look for Scheduler in Base
Don't use blocking writes from the Scheduler
Fix build on Linux
Fix write return value for UTF8
Address Jeff's comments
Make async write close the stream on error