Fix mmap_bitarray; extend it to Windows

Also add tests.
Fixes breakage introduced in d4d433d756
Pkg docs: fixes for proper display via help()

* Removed the Pkg prefix in the definitions, since otherwise
  help() doesn't work
* Added preamble to make clear Pkg functions are not exported
* Linked the page in stdlib index
* Updated helpdb.jl

Together with the actual writing of the docs in
468c0297f67e16a2d47983c2a7b31a3bcd30daed, this
closes #4696.
Update docs for previous change in ambiguous function warning.
Improve help()

* Discriminates between functions from different modules
  with the same name when calling help on the function itself
  (fix #4697)
* Attempts to prepend "Base." to function names
Fix #4709
rename home() => homedir().

https://github.com/JuliaLang/julia/commit/456fb0a1d162de1b45bac22a48ab7580a43573ee#commitcomment-4494896
doc/stdlib: homedir()
docs: replace usages of home() with homedir().
Merge pull request #4705 from JuliaLang/cb/bitmmapfix

Fix mmap_bitarray; make it available in Windows
Speed up (and test) sparse matrix-vector multiplication
test/bigint: fix failure on 32-bit system
Fix code for cholmod < 2.1.

It is field IPerm which was added in cholmod 2.1, not field Perm.
Merge pull request #4711 from GlenHertz/patch-7

Update docs for previous change in ambiguous function warning message.
fix #4710, export/document searchindex and rsearchindex
improve printing of kw expressions
Merge pull request #4712 from JuliaLang/cb/helpfix

Another attempt at fixing #4697
fix #4718, Zip iterator was impure

this also makes it faster, and special-cases zipping 2 iterators
other iterators updated to be immutable
add eltype methods for iterators
a small inlining improvement that makes Zip2 faster
revert change to splitline benchmark. ref #4724