MinGW fails to compile due to warnings

[asmaloney]

(From here: #245 (comment))

I think his fix in CRCpp (which is what I used here) won't work for MinGW.

@UshnaGul - can you try changing the checks in CheckedFile.cpp from

#if defined( WIN32 ) || defined( _WIN32 ) || defined( WINCE )

to

#if defined( _MSC_VER )

That should turn off the pragmas MinGW doesn't understand. Not sure if it will throw other errors though.

[UshnaGul]

I did that and it appears to be fixed. But I did the same thing in another place as I had a similar error and now I am running into more issues:

E57SimpleData.cpp:

Errors:
undefined reference to `e57::Data3DPointsData_t::Data3DPointsData_t(e57::Data3D&)'

[asmaloney]

I don't know how to fix this since I can't compile with MinGW and it seems like it's a bigger problem (whac-a-mole!).

I'll check in a couple of fixes and leave this issue open in case someone with MinGW wants to fix it.