Add random() for openarrays
More robust implementation for finding the beginning of the stack.

This patch inserts an extra stack frame above the function that
calls the actual Nimrod code and ensures that a reference to this
frame is stored as the stack bottom.
Add newSeqWith
Add automatic MAP_POPULATE flag for opening read_only (MAP_PRIVATE) and shared (MAP_SHARED) mmap files.
Do not automatically use MAP_POPULATE for opening mmap files.

Adds use_map_populate keyword to memfiles.open and memfiles.mapMem
to govern MAP_POPULATE use. This is set to false by default.
Revert "Do not automatically use MAP_POPULATE for opening mmap files."

This reverts commit cba75db4e36b3af0d39b5717141a971e6d558554. The prior
commit yields a compiler error 'error: lvalue required as left operand
of assignment; MAP_POPULATE = ((int) 0);'. So for now this branch
*always* adds MAP_POPULATE when using the open and mapMem procs.
Only try to import MAP_POPULATE on Linux, define flag as 0 otherwise.
Documents nimcache file naming scheme. Refs #852.
Makes ios example work again with new paths. Refs #852.
Corrects description of nimcache file naming. Refs #852.
Make device and file ID's public.

Added the isHidden() proc
Made the code actually work, updated the docstring to point out that the given file path must exist *and* be accessible from the current working directory of the running program.
Move newSeqWith to sequtils
Merge pull request #1405 from boydgreenfield/add_mmap_map_populate

Add mmap map populate
Merge pull request #1417 from gradha/pr_852_nimcache_naming

Documents nimcache naming and fixes ios example
Merge pull request #1403 from def-/newseqwith

Add newSeqWith
asyncio compiles again
Merge branch 'devel' of https://github.com/Araq/Nimrod into devel
asynchttpserver compiles again; made some tests green
made some tests green