Added the hidden `chm_factorize_p` function

This function, which calls `cholmod_factorize_p`, allows for updating
the factorization for A + beta*speye(size(A)...) without explicitly
forming the sum.  This is convenient and saves a bit of time in some
of my work.
Change the URL of libuv submodule.
Create a header for platform identification.
Building libsupport with NMake and Intel C++ Composer
Fix incorrect indentation.
Collects all linear algebra errors into linalg/exceptions.jl
Fixes import locations
Remove the libuv submodule URL change.
Merge pull request #2964 from JuliaLang/jh/linalg-except

Collects all linear algebra errors into linalg/exceptions.jl
Move all aupd/eupd code to arpack.jl
Move ARPACKException to exceptions.jl
cleanup range searchsorted methods, remove redundant hist methods
Merge pull request #2927 from dmbates/master

Add a hidden convenience function `chm_factorize_p` to LinAlg.CHOLMOD
fix #2971
Merge pull request #2970 from simonbyrne/ranges

cleanup range searchsorted methods, remove redundant hist methods
Use '\x1B' as escape character for all compilers.
Fix incorrect file protection flags on Windows.
Add a DataStructures module with PriorityQueue and heap functions.
Rename DataStructures to Collections. Document.
Export Collections, not DataStructures.
"DataStructures" to "Collections" in a comment.