Add setFilePointer

[alexbiehl]

For a project of mine I need to be able to seek a file.

Description

This adds another foreign import to SetFilePointerEx and calls that.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [x] I have updated the documentation accordingly.
• [x] I have not added a new Haskell dependency.
• [x] I have included a changelog entry.
• [x] I have not modified the version of the package in Win32.cabal.

[Mistuke]

Thanks @alexbiehl , just a minor comment, could you name the function setFilePointerEx instead. Since we don't include documentations in the library we want to retain the exact name as the function on msdn. So it's easier to google.

[Mistuke]

Thanks @alexbiehl