Some renamings for consistency as discussed in #2593.

Eigen -> EigenDense
eigenfact -> eigfact
Hessenberg -> HessenbergDense

Includes doc updates for linalg as well.
Separate sparse matrix documentation into a separate file.
Add sparse.rst, which I forgot to add in the last commit.
Allow overriding LLVM Targets
Avoid using bool() in the call to nnz.
bool(Complex) gives InexactError, which causes a whole bunch of stuff to break
Also add a test for sparse complex matrix construction.
Merge branch 'master' of github.com:JuliaLang/julia
Some updates to the laplace benchmark.
Remove old median example.
correct sprintf/printf doc
Merge pull request #2599 from ihnorton/master

doc correction: sprintf/printf
Include documentation on sparse factorizations.

Also some housekeeping changes.
Fix imports from LinAlg, not Base
fix typo
Merge pull request #2604 from WestleyArgentum/patch-1

fix typo
Force 32-bit compilation on Travis
Try to make sparse tests pass on travis.
Fixes calls to LAPACK.stebz

Fixes crash in eigenvalue computations for SymTridiagonal matrices
Merge pull request #2609 from jiahao/issue-2606

Fixes calls to LAPACK.stebz
Merge branch 'master' of https://github.com/JuliaLang/julia into travistest
Merge pull request #2605 from staticfloat/travistest

Force 32-bit compilation on travis