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

Ref: #8760
parametric typealias additional explanation

I added some text to clarify a point that stumped me about parametrized types and typealias.
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.
nicer alignment of MathConst arrays
replace VLA with alloca for MSVC
print type user-defined type names fully qualified.
Fix help for operators starting with a dot

This fixes #8903 and supersedes #8922 (cc @hayd). Basically, when you pass a function to the help system (instead of just its name), the system can go through all the modules and only returns those methods that actually extend the same function.  The way it does this, however, is a little hacky... using string concatenation to combine the function name with the module names, and then splitting it back apart again on dots to get the functions within each module.  This simply improves the splitting logic with a regex to handle the leading dot.
Fixes space completion in paths in the REPL like: cd C:\\Program\ Files\\
faster randn with ifelse
Merge pull request #9126 from JuliaLang/rf/randn-ifelse

faster randn with ifelse
Add performance note in the use of ifelse.
Remove some trailing whitespaces.
Add some of the recent RNG updates to NEWS.md.
Add SubArrays to NEWS.md
Add URLs for the RNG updates.
Update mailmap
fix #9117 (add DLLEXPORT to jl_base_ctx), and make stack switch more efficient (avoid the double longjmp)