Pkg2: prefetch all available versions of installed packages.

This is necessary to correctly computed if a package is fixed and
its installed version in all cases. This should avoid the warnings
that are currently printed when doing an update about metadata out
of sync.
Pkg2: consistent info message capitalization.
fix make error when ARCH=i386
fix #3613
Merge branch 'master' of github.com:JuliaLang/julia
Merge branch 'master' of github.com:JuliaLang/julia
Pkg2: suppress insistent output from `git remote update`.
Pkg2: fix missing key bug for update() with unregistered packages.
optimize ... when delegating an arglist. ref #3440
Merge branch 'master' of github.com:JuliaLang/julia
Pkg2: better info messages during update, improved ordering of ops.
Pkg2.clone(url): clone an unregistered repo in .julia and resolve.
avoid redundant re-loads out of GC frame. ref #3440
happens to make sparse mul faster; #942
Merge branch 'master' of github.com:JuliaLang/julia
cleanup some windows errata
Pkg2: an installed package is any directory besides METADATA and .*
Merge branch 'master' of github.com:JuliaLang/julia
Merge branch 'master' of github.com:JuliaLang/julia
fix perf regression in calls to jl_array_ptr
fix #2915, BigInt memory leak