Pkg: move DEFAULT_META and META_BRANCH into top-level pkg.jl file.
Merge branch 'master' of github.com:JuliaLang/julia into jb/vararginline
disable one of my changes that turns out not to be necessary to fix #4374,
erring on the side of caution
fix a suboptimality in the t-function for apply_type (involving tuple types)