Windows: Don't test ispath on deleted file or dir

These are failing with "stat: operation not permitted (EPERM)". There may still be
file handles open so the unlinked file and removed directory cannot be stat-ed.
Remove UNDOCUMENTED.rst from docs
cast to unsigned char for each use of isspace
REPL: fix history_prev

Was broken by tracking the wrong key_repeats.
This introduces a function to temporarily stack away the key repeats
counter.
Bump Rmath
Merge branch 'master' of github.com:JuliaLang/julia
Bump Rmath
Fix clean-dsfmt build rule. Bump Rmath.
Update editors section of README.
Merge pull request #7414 from JuliaLang/cjh/del-undoc

Remove UNDOCUMENTED.rst from docs
Dimension check in gemv! plus tests of same
Merge pull request #7471 from JuliaLang/db/gemv

Dimension check in gemv! plus tests of same
Merge pull request #6144 from tkelman/patch-2

Windows test failures in file.jl: "stat: operation not permitted (EPERM)"
add direct support for more integer types in iround. fixes #7441

also add more Float16 -> Integer conversions
Merge pull request #7472 from tkelman/isspace-uchar

cast to unsigned char for each use of isspace