Set zero offset in mmap_array to zero(FileOffset)

Fixes [#5633](https://github.com/JuliaLang/julia/issues/5633)
Proper error bounds on Cholesky factorization

Implements two error bounds from [LAWNS 14](http://www.netlib.org/lapack/lawnspdf/lawn14.pdf) concerning the elementwise reconstruction of a matrix from its Cholesky factorization, and the error bounds of performing a linear solve using the Cholesky factors. (#5605)
allow remote evalfile to return a value. fixes #5648
Merge pull request #5639 from rickhg12hs/fix-sharedarray

Fix #5633 -> Set zero offset in mmap_array call to zero(FileOffset)
prevent unnecessary copy in converting UTF32String to same type