Enhance Timers to ensure compatibility with more Windows versions

[randomdude]

I've done some work to the Timers.py plugin to enable it to function on different builds of Windows.

I've updated local type definitions of _KTIMER_TABLE_ENTRY to work on both 32 and 64bit targets, and ensured they don't get applied if they aren't needed (ie, if the OS overlay already defines these structures). I've also added more signatures for different versions of windows.

I also found that the DPC validation code doesn't work properly in some older Windows versions, and so I've commented it out. I've left the code in there because filtering on valid DPC is a useful feature, and it works on most versions of Windows.

I've tested this code and found it working on the following builds:

• Win 10 build 15063 (32- and 64-bit)
• Win 8.1 SP1 (32- and 64-bit)
• Win 7 SP1 (32- and 64-bit)
• Win Vista SP0, SP1, SP2 on x86
• Win Vista SP2 on x64
• Win XP SP1, SP2 on x86
• Win XP SP3 on x64
• Win server 2003 SP0, SP1, SP2 on x86
• Win server 2003 SP1, SP2 on x64

Hope this is useful!