accurate sind, cosd functions
`using Nonexistent`: better behavior loading unfound names.

    julia> using FooBar
    ERROR: FooBar not found
     in require at loading.jl:45

The core change is that `find_in_path(name)` now returns `nothing`
when `name` isn't found and various functions that call it must
check explicitly for `nothing` as a return value and throw an error
as appropriate. In particular `require` and `reload` now raise an
error instead of just forging ahead trying to load a file we know
doesn't exist, which resulted in less-than-clear error messages.
fix #4080, don't try to deepcopy Tasks
Revert "Fix beta function for BigFloats"

This reverts commit 5b3745294c8cfd4bb3c33ff2482ae256f5e138b7.
add lgamma_r for BigFloat, make beta() work
doc: patch up the development docs for the Pkg rename [fix #4081].

Obviously better docs that don't depend on Pkg1 are in order.
Merge branch 'master' of github.com:JuliaLang/julia
Merge pull request #4079 from simonbyrne/trig

accurate sind, cosd functions
small formatting changes to sind/cosd improvements
fix intermittent crash at end of tests due to uninitialized req->data
fix #4066
Be conservative about a couple more ->data fields

you never know when the garbage collector might run, so get these set ASAP
Also make sure the ->data field is set properly for tcp sockets
fix another intermittent segfault

before I failed to fully fix the deserialization bug where constructing
an Array needs to look at the element type, but the element type might
not be fully initialized yet.
Merge branch 'master' of github.com:JuliaLang/julia
formatting fixes
Fix test for #4075 on 32-bit platforms
Pkg: fix `make test-pkg` largely broken by relative JULIA_PKGDIR.

Calling Pkg.Dir.cd() in a nested fashion unavoidably breaks for a
relative JULIA_PKGDIR, which is no good. This avoids such situations
but is kind of a mess. The __fixup, _fixup and fixup thing is awful.
@loladiro, this could really use some attention -- why are there so
many fixup methods? This should basically never be called by users
except as Pkg.fixup(). However, this really should be handled more
cleanly in general. One approach would be to have an outer module in
which only cd'ing and calling the core functionality happens, but it
might be even better to just refactor this so that one never cd's.
fix #4083: Pkg.intalled(pkg)
Merge github.com:JuliaLang/julia