Fix MAX_PATH for standard IO

Real support of native System.IO is not for 250, but for 247. While it 250 all paths in between are not processed correctly.
Support for x64 IntPtr added

Originally IntPtr is being converted to Int32, what is sometimes wrong in x64 bit environment.
History update
Merged master
[Update] Issues fixed from source repository
History update
[Update] Ranaming; bug fixing
History update
Fork description update
Link to source added
Spelling fixes
History update
[Update] IOHelper tests fixed
[Patch] Reverted naming to original
[Patch] Binary file rebuilded
[Patch] Redundant dll removed
Merge pull request #3 from SergeyFilippov/patch

Patch from ZetaLongPathEx