annotate f as Function for map, map!, mapreduce, reduce
change the annotation of f from Function to Union(Function,DataType)
added rsplit. fixed rsearch for a case when both string and pattern are empty.
incorporated comments and corrections
Fix process chain handling in spawn

Fixes #3488
Reset SIGPIPE handler in child processes

Allows things like run(`yes` |> `head`) to not hang.
Introduce abstract type Callable
Merge pull request #3480 from lindahua/annot_funs

Annotate function arguments with Union(Function,DataType)
use .- instead of bsxfun in var
Merge pull request #3491 from lindahua/var_quickfix

use .- instead of bsxfun in var
buffered writedlm. print substring calls write substring. fixes #3483
faster utf8 readdlm
Merge pull request #3492 from tanmaykm/readcsv

buffered writedlm. substring print invokes write. fixes #3483
closes #3437. Also rmprocs can now accept an array of pids too.
Merge pull request #3493 from amitmurthy/rmprocs

closes #3437. Also rmprocs can now accept an array of pids too.
pkg2: use package caches as canonical version history in Read.

Also, be more verbose when cloning repos as otherwise this just
appears to hang for a really long time.
pkg2: impement Pkg2.update(), add Pkg2 to system image.
specialize promote_shape for (Int, Int) and (Int, Int)
Merge pull request #3498 from lindahua/promoteshape2

specialize promote_shape for (Int, Int) and (Int, Int)
specialized methods for fast reduction of tuples
Merge pull request #3499 from lindahua/tuple_reduc

specialized methods for fast reduction of tuples
Merge pull request #3477 from tanmaykm/rsplit

added rsplit. fix rsearch for case when both string and pattern are empty