Initial work to wrap dbgeng.dll with FFI. The key to the project is the FakeCOM class, which allows
COM objects to be accessed through Ruby without the hefty comtypes style approach of registering
DLLs and such.

Currently working:
* General wrapping, non-callback based, local and remote (via DRb)
* Callback support, in local process only
* IDebugBreakpoint wrapped via Breakpoint class
* x86 in MRI and JRuby
* x64 in JRuby with the 64 bit debugging tools

To do
* Get callbacks working via DRb

Alpha release, "it works for me" quality.

NOTE: Tested with / uses headers from version 6.12.2.633. Using different
versions of the debugging tools can cause random access violations. Set the
DEBUGGER_PATH environment variable to the root directory of your debugging
tools, if you've installed it somewhere other than the default for the MSIs
from here:

http://archive.msdn.microsoft.com/debugtoolswindows/Release/ProjectReleases.aspx?ReleaseId=4912