MinGW fails to compile due to warnings

(From here: https://github.com/asmaloney/libE57Format/issues/245#issuecomment-1518088249)

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

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

to

```cpp
#if defined( _MSC_VER )
```

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

Start in CheckedFile.cpp and inspect the platform checks around the compiler pragmas. Build the library with MinGW after making the requested compiler-specific adjustment; done means MinGW no longer fails on unsupported pragmas or related compilation errors.

Written by the indexing model from the issue text.