Solved bug with 64 bit regex option

RegexOption was selected to compile or not if the operating system was
32 or 64 bits. This is wrong because it is the mode of the process that
decides the speed problems for 64 bits (32 bit process can run on a 64
bit OS). This can easily be checked with the size of an IntPtr (4 or 8),
thus removing the entire neet for class PlatformType (and thus two
DllImports, which is a goal for me)