compat: no MmapIO for windows 7

[HongBinYu-hub]

Ensure win7 can be precompiled
Win7 and below systems use IOStream method to ensure pre-compilation correct.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a0d0730) 85.94% compared to head (499c1f0) 85.92%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #509      +/-   ##
==========================================
- Coverage   85.94%   85.92%   -0.03%     
==========================================
  Files          31       31              
  Lines        4213     4213              
==========================================
- Hits         3621     3620       -1     
- Misses        592      593       +1     

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[johnnychen94]

I really think you should change the default value for iotype (everywhere) to be DEFAULT_IO_TYPE, where

# Windows 7 doesn't support mmap, falls back to IOStream
const DEFAULT_IO_TYPE = if is_win7()
    IOStream
else
    MmapIO
end

is_win7() = Sys.iswindows() && Sys.windows_version().major <= 6 && Sys.windows_version().minor <= 1

The current version doesn't really fix anything: what makes the default and most commonly used jldopen usages broken is still broken.

[johnnychen94]

@JonasIsensee Are you okay with this compatibility patch? For some reason, we (Suzhou Tongyuan) need to keep compatibility with some "strange" platforms, e.g., windows 7.
We prefer to contribute upstream first, so here's the patch.

If you don't want to get this patch in, we understand, and we'll instead start to maintain our internal fork version.

[johnnychen94]

I think it should be

Suggested change

	JLD2.MmapIO
	MmapIO

[JonasIsensee]

@JonasIsensee Are you okay with this compatibility patch? For some reason, we (Suzhou Tongyuan) need to keep compatibility with some "strange" platforms, e.g., windows 7. We prefer to contribute upstream first, so here's the patch.

If you don't want to get this patch in, we understand, and we'll instead start to maintain our internal fork version.

I apologize for the late reply..
I like this approach:
const DEFAULT_IO_TYPE = if is_win7()

[johnnychen94]

Thanks for merging!

I'll use my privilege to make a patch release #514