This was a MinGW-specific, non-MS-DDK/WDK-compatible define, that was
used to mark NTOS kernel/hal exports, instead of NTSYSAPI etc.
We have since fixed that, and changed the way Freeldr (and rossym)
manages these, see commits:
186c8b72d (r16028), 51f0dfd30 (r17651) and 526efd2ee (r24359)
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
