KD64: Raise to HIGH_LEVEL when entering trap
KDBG: lower to DISPATCH_LEVEL when applying IRQL hack & use a worker thread to load symbols
KD&KDBG: Actually unload symbols when required
- Always include kd64.h
- Change KdpPrompt() prototype to be compatible between KDBG and _WINDK_
- Rename KdComponentTable to KdpComponentTable to prevent a conflict
- Add some functions stubs and global variables