THREE BYTES ON X86

Analysis:
=========
The macro uint3korr reads 4 bytes of data instead of 3 on
on x86 machines.

Multiple definitions were created for this macro for
optimization in WIN32. The idea was to optimize reading of
3 byte ints by reading an ordinary int and masking away the
unused byte. However this is an undefined behavior. It will
be an issue unless users are aware of allocating an extra
byte for using this macro.

Fix:
====
Removing the definition which reads 4 bytes of data. The
only definition of this macro would now read just 3 bytes
of data thus prohibiting the usage of an extra byte.

Note:
=====
This is a backport of Patches #5 and #6 for Bug#17922198.