partial support for out-of-tree builds of julia src
Emphasize how `isimmutable` works for types.

Ref: #8760
Ignore `@inbounds` when running Pkg tests on Travis
implement float vs int comparisons in Julia
modify int-float comparisons to fix #9021.
parametric typealias additional explanation

I added some text to clarify a point that stumped me about parametrized types and typealias.
IteratorsMD: remove ambiguity resolution for SharedArrays
IteratorsMD: handle 0-dimensional arrays properly
Bump PCRE to 8.36
The GCC 4.9 patch is now included upstream.
Merge pull request #9062 from JuliaLang/pcre8.36

Bump PCRE to 8.36
Improve wording of docs for middle()

Cf. #9032.
Merge pull request #9020 from JuliaLang/teh/travis_checkbounds

Ignore `@inbounds` when running Pkg tests on Travis
Use a tarball instead of git for checking out LLDB.
Don't forget to download LLDB, and make python2 hack more compact.
Ignore LLDB deps, and add some checksums.
Remove unused LIBCXX_OPTIONS.
`rand` sampling from an array accepts an optional rng

Fixes #5978.
IteratorsMD: allow AbstractArray methods to be overriden

Any AbstractArray type that wants to override an indexing methods would
have formerly run into trouble:

    next{T,N}(A::SomeArrayType{T,N}, state::CartesianIndex{N})

would be more specific in the first argument, but (because
CartesianIndex{N} is less specific than CartesianIndex_$N) would be
less specific in the second argument. So there was no way to avoid
a method ambiguity warning.
IteratorsMD: document eachindex and add NEWS.md item
clarification suggested by @ivarne