Add libunwind patch from Pyston
beginswith, endswith accept Chars
more efficient setindex for sparsematrix
replaced splice! with deleteat!
Update C/Fortran microbenchmarks to new dSFMT path
Relax type restriction on isnan/isinf/isfinite of arrays
Merge pull request #6792 from JuliaLang/sjk/isnan

Relax type restriction on isnan/isinf/isfinite of arrays
Expand macro documentation

These changes are based somewhat on the [discussion on the julia-users list](https://groups.google.com/d/msg/julia-users/YTZM3Biy-rM/m0orpSjQ8RIJ) and somewhat on my own stumbling points as I was learning how macros worked.

Here's the motivation behind these changes:

* Stress that macros *return* an expression to be evaluated, and hopefully make it look like they're less magical to newcomers. Make `return` explicit in the examples, so it looks less like textual substitution and more like a mapping from exprs to an expr.
* Provide an example where the macro is more than just return an expression. The changes to `@assert` since the original documentation was written make this very natural without needing to contrive another example.
* Use function such as `macroexpand` and `dump` in the examples to help make things more concrete and give users tools to play with.
* Make the hygiene section introduction a bit more clear, with an emphasis that the only thing it needs to worry about is the returned expression.

I think this should help folks 'get' macros a bit quicker. I hope.
fix #6793
Fix PriorityQueue(ks, vs) constructor
Add test for PriorityQueue(ks, vs) constructor
fix #6798
Merge pull request #6796 from wsliang/pq_constructor

Fix PriorityQueue(ks, vs) constructor
Update linalg.rst

Complemented linreg() documentation
attempt to fix #5574
Update ARPACK to 3.1.5
Merge branch 'master' of github.com:JuliaLang/julia
Temporarily disable ARPACK's internal tests.

On Linux, the tests will pick up the old libarpack from
JULIAHOME/usr/lib and fail due to a bug in the old libarpack.
Disable the dnsimp test of ARPACK also, as it is not built anymore.
Disable the dnsimp test of ARPACK also, as it is not built anymore.